> Take Musk away, who is investing in expensive, risky stuff with actual potential to change things?
Your point is mostly valid, however there are others.
Gates & Buffett will ultimately pour a collective ~$300 billion into education and health. That includes attempting to wipe out various diseases entirely and eg inventing new ways to deliver vaccines cheaply - just about as important to humanity as most anything else we could be doing. Gates is also putting billions into new high-risk energy technology over time, far more than Musk put into starting SpaceX and Tesla.
Jeff Bezos will probably put tens of billions into space over decades, ultimately far exceeding the investment scale of Musk in that arena (whether he'll have results worthy of that investment, is yet to be decided).
Paul Allen - his estate now - has and will put considerable resources into researching the brain over time. Beyond that he put hundreds of millions of dollars to work in other high- risk scentific endeavours that may yield large results over time.[1]
Eli Broad has poured immense resources into the Broad Institute (a billion dollars inflation adjusted), a partnership between Harvard and MIT that has already made a huge impact by blazing the path re CRISPR. The Broad Institute is one of the premiere scientific institutes on the planet.
Larry Page is putting resources into flying vehicles. Not a huge amount of money based on his $55b net worth; non the less an interesting technology pursuit that could make a dent in our transportation systems.
Sergey Brin - on a personal mission - is attempting to combat Parkinson's, which afflicts 10 million people around the world. If his funding makes a difference in curing Parkinson's, it'll be a big deal and it's certainly a high-risk pursuit.
Sean Parker has been funding some of the first attempts at getting into trials with CRISPR. The definition of high-risk with the potential to change everything, not to mention very expensive.
MacKenzie Bezos, in her declaration in relation to the Giving Pledge, has said she'll give until the $40 billion is gone. Who knows what good she may accomplish, probably in areas of education, health, equality. She seems to be a very smart woman, so I would suspect she'll do something meaningful. That type of investing is typically high-risk and with the potential to change things.
Gordon Moore has spent his retirement figuring out ways to give away his (formerly) $20 billion fortune.[2] Including pushing $1.4 billion into science grants and $1.5 billion into environmental conservation efforts (I consider that arena to be high-impact, even if it's not as sexy as a starship). He has put $200 million into the Thirty Meter Telescope.
[1] https://www.philanthropy.com/article/Paul-Allen-s-2-Billion-...
[2] https://www.moore.org/programs