Musk, Bezos, and Gates would have access to all of the funding in the world for any future ventures. What the government could do is lower taxes on everyone else.
Nobody is talking about "leftist politicians."
I am suggesting something that might actually get the middle class, or those aspiring to join the middle class, to support and vote for the idea. I think it's pointless to talk about more radical concepts like a wealth tax or UBI without considering how such a thing could be made appealing to a majority of voters.