Bill Gates also gave billions of dollars to the world for free, it's just a question of which one is more praiseworthy. I could be convinced Gates was not more impactful than Salk, but he's definitely in the running for top 100 best overall human beings in terms of positive impact on the world, in stark contrast to the claim that tech billionaire have contributed nothing
In fact the world didn't have this money before. Maybe this is the first time you've encountered the idea that the economy is "positive sum" so think of it like this:
Is the value of everything in the world higher or lower than it was 1000 years ago? If it's higher, how did it go up?
Maybe you need to do a quick Google on monetary policy 101 and how money is created. You seem to not understand the basics here.
While you're at it, consider what portion of MS success is directly attributable to Bill Gates and not the many thousands of other people involved in the company and code it literally copied from open source projects. Not to mention the extreme anti-competitveness of MS and their aggressiveness in suing and shutting down other companies, and other negative externalities they generated.