A few things:
They def didn’t lose profit over Zayn leaving. Not only did album/song sales increase, I will also offer anecdotal (read: not to be taken as seriously) proof in the form of myself rushing out and buying, like, a hundred dollars worth of shit with his face on it, for fear that it was now all limited edition and 1D’s days were themselves limited. A bit extreme? Maybe, but it’s 1D. If I did it, you can bet your ass a lot of others did, too.
I talk about the profit bump they experienced in this here post. Because they definitely, definitely did experience one. And since OTRA sales had been flagging behind previous tour sales, I can see why they timed this the way they did. I mean, we learned from the Sony leak that they were expected to take a hit to profits this year, right? Boybands have burnouts. So a more proactive team (say, the as-yet-unclear New Team) had an incentive to combat that burnout, since they’re inheriting 1D and all the potential revenue therein.
And what better than a dramatic split? It’s gotten such intense media coverage–largely sympathetic to Zayn, by the way, which is new–that I feel comfortable calling it the entertainment story of the year (though Bruce J’s transition is def up there).
Finally, the idea that Zayn wanted to leave is…I guess I don’t understand where that idea came from, really. What makes you think that? Is it how smiley-happy he was around that time? Is it how involved and engaged he was on-stage and in the fandom (using fan art as pictures on his Twitter, etc) right before he left? Is it how he talked about enjoying a more involved role in the album writing process during the NBC special? Or is it a bit of historical revisionism you picked up from a blog you trust who told you that was how it was?
I’ve offered you some thoughts, and I’ve offered you evidence to back up those thoughts. Hopefully that helps.