My friend (who completed a computational biology PhD but was dismayed by the small likelyhood of being able to do meaningful science and left to do a ML based startup) has taken the route of becoming independently wealthy himself and then privately fund researchers he personally knows with his own wealth.
I feel like that would only work if many thousands of people had that attitude because the likelihood of a single person becoming independently wealthy is very small. Even if your friend was successful he would only be limited to assisting in a small number of scientific advances.
Wouldn't it make sense for your friend to try and organize a group of people with similar goals so everyone can work together to achieve them?
This also describes David E. Shaw, who was denied tenure by Columbia University. He now spends most of his time at D.E. Shaw Research, where he basically does what he would have been doing as a tenured professor anyway.
One way to circumvent a broken system I guess.