But by not quitting it's clear that he himself doesn't really believe

I’m not saying I’d press a button that had a 50/50 chance of ending humanity vs giving me generational wealth, but … I can see how someone would get there? There are percentage odds and payouts to match all risk appetites and valuations. Anyone claiming they wouldn't press the 1 in quadrillion chance button for 1bn dollars is probably not telling the truth, and after that, we're just haggling about percentages.