1) more money is not necessarily a goal for these people - it's what for they want more money and why they believe they can spend it better than everyone else (regardless if they truly can)
2) in a post-AGI world money may be an obsolete concept
A proxy yes. But not everyone leverages it that way. So it really depends. Some do just want to hoard as much as possible, others want to lobby, others want fame, others want legacy.
Money helps with all those, but will not passively do that stuff.
Of course it's money. He is a billionaire. What do you think it's about?