I thought the reason people side with Depp is because there are recordings of Heard mocking him for reporting abuse and admitting to hitting him, that he initiated the split, and that she gave an op-ed that suggested he was the sole abuser.

Basically all of this analysis relies on ignoring a bunch of evidence and reading into what Heard's said. There is a shockingly long explanation of this point by point, something which is necessary only because of the time it takes to detangle "Heard sounds shifty". Remove the suppositions, and it really just sounds like Heard is trying to save her relationship.

Secondly, primary or retaliatory, there's a clear imbalance of power. This is a big part of what "me too" was about. It seems as soon as you're of legal age, all manner of coercive power become meaningless to the public. "Me too" was about "well, no, I wasn't necessarily raped as such, but there was a clear power imbalance that pushed me into decisions I wasn't comfortable with". It also discussed the idea of "the perfect victim", where women essentially get the blame in a two-sides issue. IIUC Heard was barely upper middle class, and Depp has an enormous pool of wealth. There's a clear power imbalance here.

Thirdly, and this goes back to the "I'm not on either side" part, the less you know the more susceptible you are to the organised campaign against Heard. That's why people do these memes. That's why I ended with: well if it's both sides are bad, then why is Depp somehow beloved and forgiven and Heard is still mocked several years later?