Tina, Queenie, and Newt all have good reasons to become Grindelwald followers
That’s what makes Grindelwald so seductive. His platform is actually one that makes sense to the main players on a personal level.
1) Tina - Tina suffered a lot as result of the International Statute of Secrecy. She breached the law to defend a boy from physical abuse, even though she had the power to stop it, and she took a huge fall for it (demoted). The law demanded that she stand by silently and allow the boy to suffer. If Grindelwald had his way, Tina would have been able to freely use magic for a lot more good. As, historically (or in folklore), witches and wizards mingled a lot more openly in Muggle society, and often served as advisors/healers. Muggles stopped benefitting from having wizards in their midst. We see this with Tina, who’s not allowed to help a (presumed) Muggle.
2) Queenie - The Statute of Secrecy has been taken to such an extreme in America that No-Maj/Wizard fraternization is forbidden. If Grindelwald had his way, Queenie would be able to freely pursue a romance with Jacob, who she’s fallen hard for. As it stands now, Jacob had to be Obliviated, and she’s breaking the law to rekindle that romance.
3) Newt - Magical creatures were once feared and hunted by Muggles, and played into a lot of the anti-magic hysteria that led to witch burnings and persecutions. However, under the International Statute of Secrecy, wizards of the ‘20′s seem more keen on exterminating magical creatures themselves as they’re such a liability. During Newt’s time, we see that many species of magical creatures are on the brink of extinction, presumably having something to do with the Statute. If Grindelwald got his way, creatures would be able to live freely, and wouldn’t be the liability wizards currently consider them to be. On the other side of the coin, the Statute seems to have been the main reason why there are so few Obscurials anymore, so Newt certainly walks on the edge, as far as where his motives could fall. Perhaps Newt is where we can most starkly see the Statute as a lesser-of-two-evils compromise.
Just some food for thought!