Sounds like AI psychosis. A whole lot of doom and gloom with no evidence. The same thing people have been claiming is "6 months away" for years. Yet we can barely get agents to code in a reliable way, or write articles that don't look terrible, much less be "superhuman". Let's maybe get them to be as capable as a human first, and not just a complicated party trick/tool.
"Revolutionize any field overnight" - Hand-wavey nonsense.
"Acquire real power and resources" - Only if the humans that connect AI to things allow that to happen (which they will, but it's still not in the AI's ability to take things we don't give it. we are still in control, which is the bigger problem than "smart AI bad!").
"The people building AI earnestly believe that it could kill us all by the end of the decade ... No other human activity poses this level of danger." - Bud, there's these things called nuclear weapons, that could end life on the planet, controlled by a few psychopaths with nearly unlimited power. Been around for a while. Nothing that AI knows isn't pulled from books and the internet, so whatever dangers it's aware of, you could already know via other sources. Cybersecurity is going to be incredibly important in the next decade, but the same tools that attack can defend (just don't use a US model that got its balls cut off by the government).
"At OpenAI, many have not deeply internalized the civilizational stakes. At Anthropic, the stakes are well-understood, but they are locked in a race to get there first - they believe no one else will act responsibly, so they must do it themselves, despite the risk." - The other guys will make nukes, so we gotta make nukes first! Which, while a crappy justification, isn't untrue. Bad people don't stop making weapons just because you refuse to make your own.
"I don’t feel like we’re on track to prevent a global race" - Nobody in the world could stop a global race, it's too late. Everyone knows how to make them, train them, improve them. Everyone knows they're useful - not only for general work, but also warfare. Everyone knows that every nation state will require their own sovereign AI capabilities for both defense and offense. There is no putting the genie back in the bottle. If you think OpenAI and Anthropic are the only legitimate players here, you don't know what you're talking about.
"Should you put your head down because “it’s happening anyway” - or take this moment to call for different conditions?" - You can call for different conditions all you want. Nobody will do what you want just because you ask them to. Change happens through action. By leaving one of the places that you could actually make a difference, you removed any power or agency you had. You cut your own legs off.
I'm not saying this guy shouldn't have quit - always do what you need to do to protect your own mental health and wellbeing. But these arguments are not evidence for an impending AI apocalypse. But if it were going to be an AI apocalypse, leaving and not doing anything to stop it seems less ethical.