Absolutely not a jerk. At least, not a jerk for saying "I am done, I am not finishing this, leave me alone forever."
It is not a matter of saying "suck it up" or "handle trolls better" or "get a thicker skin". Many successful game developers become targets. Those aren't just minor issues, they are repeated targets of major felony crimes, including death threats against themselves and their families, sometimes with their names, addresses, photos, and the schools they attend.
People on my team have received death threats, including death threats accompanied by doxxing attacks. It is stressful to everyone involved, including the police and FBI agents who were all brought in to investigate. It changes the workplace environment to know that your designer's kids have death threats with their pictures and school associated with them. You know the designer won't be able to focus on making the best game, no matter how much they're working they will always have in their mind the thought of their child with a target on them.
The toxic cultures that some sub-groups encourage are a horrible thing. It is something the industry does very little to correct.
Much of the casual slang used by some immature gamers, comments like "go kill yourself" for petty annoyances, are completely unacceptable in any other social context. In many contexts it would be enough to get a person fired, arrested, or face civil penalties. Many sub-groups are extremely aggressive digitally. Then there are people who engage in swatting where people have been shot, and then think it is a joke for Internet gold. But the highly toxic gaming culture not only accepts vitriol as normal, many sub-cultures of fans praise and promote the hatred, the attacks, the insults. In some sub-cultures these are not seen as the actual crimes of blackmail or stalking or harassment or criminal threats, but instead seen as a victory for their group in inducing change.
Imagine if your role was reversed. You're putting out a project, a work of passion where you invest all you have to create something amazing. And your results are hugely popular. But it is popular not among adoring fans, but fans who are quite literally threatening to kill you over your work. Fans who write the most horrible hate messages because you haven't done whatever it is that your fan imagined you would do.
At the time I hoped his leaving would make a dent in the culture, but I think it has only gotten worse.
When you fear for your life because of multiple death threats, and when the government tells you that they are actual credible threats against your life and you need to take precautions, that changes things. When that happens, I agree that it is not only a good thing to step away, but to make a big deal about the crimes as well. He risked (and received) even more threats due to his visible decision to say the behavior is unacceptable. In that regard he has my complete respect and appreciation.