Musk is a nice example. He probably would've started the same, but Tesla and SpaceX wouldn't have existed / been the same as today.
Remember that at some point Musk had poured all his wealth into those companies and they were one failure away from bankruptcy. If Musk had any less money after PayPal, he couldn't have done what he did.
In this alternate universe, PayPal could have morphed into PayPalphabet and spawned other companies corresponding to Musk's interests. I think that would still work fine as long as the money stayed within the company and out of executives' hands.
Yes, I think it absolutely would happen. Incentive would still be there. People won't sit around idle just because they can't make a million times more money than their peers.
Remember that at some point Musk had poured all his wealth into those companies and they were one failure away from bankruptcy. If Musk had any less money after PayPal, he couldn't have done what he did.