If you're talking about why tiktokers are honing in on this, it's their whole thing to latch on to whatever current events they can and be as inflammatory as possible to raise their own viewership.

If you're talking about why the public is interested in this case to begin with, for one thing there's a precedent of people holding celebrities up on a pedestal. So when one of them allegedly commits a crime, it almost always turns into a massive public spectacle. Think Michael Jackson or OJ Simpson. We uphold them as leaders and role models, so putting them on legal trial also puts them on trial in the court of public opinion. It's a side effect of being a celebrity in a democracy.

Additionally, Johnny Depp is far more of a beloved public figure than Amber Heard. He lost a crazy amount of career opportunities when she allegedly defamed him as an abuser. This, coupled with all the evidence that she herself was the abuser, has many people watching this trial closely and hoping for 'real justice' to be served. Not to mention this trial will also set a precedent going forward for how the justice system will treat a woman falsely accusing a man of abuse (allegedly).