Ok, while most of these don’t have companies behind them with huge revenues, most work on these projects is done by paid developers, with money coming from sponsorships, grants, donations and support deals. (Or in the case of Linux - device drivers are a prerequisite for anyone buying your product).

Developers getting paid to work on open source is a good thing. These projects may have begun their life as small hobby projects - they aren’t anymore. (And that’s probably good)