Publicizing vulnerabilities is the problem though. Google is ensuring obscure or unknown vulnerabilities will now be very well known and very public.

This is significant when they represent one of the few entities on the planet likely able to find bugs at that scale due to their wealth.

So funding a swarm of bug reports, for software they benefit from, using a scale of resources not commonly available, while not contributing fixes and instead demanding timelines for disclosure, seems a lot more like they'd just like to drive people out of open source.

I think most people learned about this bug from FFmpeg's actions, not Google's. Also, you are underestimating adversaries: Google spends quite a bit of money on this, but not a lot given their revenue, because their primary purpose is not finding security bugs. There are entities that are smaller than Google but derive almost all their money from finding exploits. Their results are broadly comparable but they are only publicized when they mess up.