Long story short;

After his divorce from Heard, he pushed a libel lawsuit at The Sun in the UK and the Washington Post here in the US. The libel lawsuit is over them labeling him a "woman beater" when they published the photos of Heard all bruised up. He claims he has to restore his reputation and his fans want The Truth™ so his good name is cleared. The first thing his cult fan base latched onto was Heard confessing that she hit him back and confirmed that the domestic violence was basically them both beating up on each other (which makes sense!).

Depp had to admit in court that his good guy brand image is nothing more but masterful PR, which is what his fans buy into. He admitted it himself too, that he has never stopped drinking or using drugs. All this came out in court as they had to start digging up dirt over who said what and who did what. He's managed to royally fuck himself with this case cause all of his dirt has come out and he don't look like this good guy/family man/whatever that his fans bought into (which really isn't a shock given we've been hearing stories of him being drunk off his ass in Hollywood for years). His court defense was to blame it all on her with the "she was doing it with me" defense.

His fans lost their collective minds when he was removed from Warner Bros' Fantastic Beasts (however no word from his fans that they paid him his millions of dollars in salary), and they want Amber Heard removed from Aqua Man 2. This all came as a result of it coming out in court, that Depp reached out to his sister working at WB and he tried to have his ex-wife removed from the set. WB dropping him is pretty much them washing their hands from bad publicity.

UK courts ruled against him and he lost his case, which means he's most likely going to lose his $50 million lawsuit against the WashPo as well, but his fans want JUSTICE and I guess they're willing to march for a millionaire celebrity.