This is such a blatant, malicious warping of the actual events.
First of all, tags used to be easier to avoid. In the old days, circa 2012, only the first 5 tags on a post were indexed to the tag feed. So, it was common practice to, for example, use the tags "NSFW, Not safe for work, adults only, porn, pornography" to eat up the first 5 tags on explicit works, then tag the ships, content, etc to organize your blog safe in the knowledge that you would only be posting porn to the porn tags.
Then the "search"new tag search" (my term, not theirs) was introduced. This was around 2014? 2013? It was before acecourse really took off, because it helped fuel a lot of acecourse's more heinous behaviours.
See, tumblr has always been a majority adult, majority NSFW website. This is reflected in the app stores' age ratings being 17+. Which, you'll notice is distinct from the 18+ that denotes "adult only" in the US. This is because anyone over 13 has always been able to register on tumblr. This was and is common practice on much of the internet today, eg facebook, twitter, youtube, etc. It's broadly accepted that children may be guests in these places, in the same way they may be guests at a sports bar on quiz night. So long as no one gives the children alcohol, the adults are welcome to drink.
But, many users had previously avoided porn on tumblr simply by not knowing where to look for it. This combined with a strict politeness about tagging NSFW for the benefit of fellow working adult users of the site, led to a small but vocal subset of users who genuinely had no idea about the porn thing.
Until the new tag search dropped.
Suddenly it was much harder to avoid porn. You needed a blacklist of some sort, which tumblr wouldn't introduce as a native feature for many years. Blacklists were critical for managing your tumblr experience in those days. Tumblr saviour, missing e, eventually the first xkit. They all addressed the need for blacklisting now that you couldn't politely avoid posting your porn to everyone.
Because, again, tumblr has always been a majority NSFW, majority adult website. Since its very inception, this has been true. Tumblr has never, for one single moment, been "for kids."
There are websites for kids, you know. Not as many of them as there used to be in like 2005. But they do still exist.
Tumblr is not and cannot be one of them.
Because tumblr has, since its inception, been "for" artists. That mission was frequently degraded, to the point that many people don't even remember this. But there was a time when the popular joke on "fandom tumblr" was that tumblr had "two continents." There was "art tumblr" and "fan tumblr," which was a known, smaller newcomer.
Today you still see echoes of that joke in the phrase "the science side of tumblr."
Anyway. Porn became unavoidable.
This shocked some of the kids who hadn't known they were using a porn website, but they generally quickly recovered because the contemporary horror surrounding the concept of sex was actively being fought in the popular culture of the time. See also: slut walks, female toplessness in the US.
More importantly. It horrified two groups of adults. The extremist christians, and the TERFs.
Extremist christians were quickly laughed off by most tumblr users, even the kids. This is because extreme christianity wasn't nearly as popular to discuss publically 10 years ago, when some dim concept of "separation of church and state" was still considered acceptable in a public space either.
TERFs, however, were mostly adult women, often queer, but just as often painfully capital-S Straight And Cis. Still. Often queer women. Queer adult women.
They had an extremely easy time presenting themselves as mentors and kindly protectors to any queer kid who stumbled into a bit of properly tagged porn and expressed discomfort.
To put it plainly, they were predatory. Their prey were queer teens and young adults desperate for guidance in a violently queerphobic world.
They nurtured the feelings of discomfort in their prey, purposely exposing them to uncomfortable and adult topics on purpose. Literally grooming these children, for real.
That is what bred the anti-porn minority on tumblr. Adult women who couldn't cope with the idea of trans people existing, and literally created controversy after controversy to ensure that there were always kids on tumblr exposed to violence, despite the best efforts of any normal user. TERFs started anti-asexual discourse on tumblr. Anti-nonbinary discourse. The entire "tucute vs truscum" mess (note: truscum literally named themselves 'scum' on purpose and now pretend they are being insulted). TERFs looking for victims underlie every single "queer discourse" tumblr has ever had. That includes anti-porn and anti-kink discourse.
And to be clear, this entire problem started with a poor decision on tumblr staff's part.
Then tumblr got sold to corporate masters, with corporate money. Unironically, the developers and staff were being held hostage and forced to be as user hostile as possible.
That included cuts to (or else refusal to properly grow and manage) the user support team who handle reports for bugs, harassment, etc. There were many years where you could send in a dozen clear and explicit murder threats including your geographic location to staff, and get no response.
So people's distrust of staff grew as they were forced to worsen everything, including but not limited to making it harder to blacklist the god. Damned. Porn.
Thus the fire remained fueled for years.
And in the mean time, political sentiment in the united states went FUCKING. INSANE. Every single basic civil right we have all come to take for granted in the US has abruptly disappeared. Now to be fair they were always tenuous, but this shit is bananas. It was done with such glee, despite the vast majority of US Americans being horrified.
But our cities were literally designed to make it as easy as possible for the military (or the militarized police) to take over, so I can see why some hesitance is warranted.
Anyway, it was in the early days of this fervor that the bills SESTA and FOSTA were passed. Advertised as a way to stop sex trafficking, they failed completely. They literally made sex trafficking worse. That's not a joke, there have been studies done.
They passed 6 months before the porn ban.
Now, one thing of note did happen during that six months.
An actual ring of child abusers sharing violent images of their victims was genuinely discovered on tumblr. This was reported to the correct authorities immediately, and handled by the feds as was appropriate.
I know this, because my moirail (yes, I am in fact that kind of homestuck fan) was the one to file the initial report.
Now, let's say you're a major corporation like, oh... verizon. You have a website that could be held liable for aiding child trafficking. It's absurdly unlikely, but the possibility exists. Your investors and business partners are breathing down your neck, including the notoriously hard to please Apple. Sex workers are pretty famously a significant part of your user base, even.
They banned porn because the US government went fucking insane 6 months earlier and no one knew yet if that shit was going to go to court.
But of course the long time anti-porn TERFs on tumblr celebrated this as a huge victory.
Meanwhile every normal person was panicking over the loss of history.
Which apparently we were right to because it's barely been 5 years and this shit is passed down like facts from on high.
The porn ban had nothing to do with your disgusting, TERF fuelled, impotent attempts to get queer sex re-criminalized. You malignant shits just happened to have the same goals as literal fascists, namely putting more people in danger while claiming it's for their own safety.
Anyway, tumblr has since been resold and that's a whole separate thing but to be clear? To be crystal fucking clear?
The goddamned US government's hatred of sex as manifested by SESTA/FOSTA caused the fucking porn ban.
Your petty little ego is, tragically, not as impressive as the imperial capital's descent into fascism.