The authors of the OSS aren’t making money but Google, Amazon and Microsoft are.
What do you think about this?
You have a FOSS tool that's awesome to work with. By yourself, you can take the time to set it up and learn how to maintain and use it. It's actually the case most of the time.
If this tool is interesting/useful enough to attract companies, they don't always have or want to have a service/person to set up, configure, maintain and debug this tool.
In that sense, companies making the FOSS tool can sell active support, maintenance and hosting, and I think it's perfectly fair here.
But Microsoft is obviously a cancer (It did not give anything really to FOSS ecosystem, just took from that), and Google is a double edged sword.
Google uses open source components which is highly advantageous for technical end users (Eg: I can run Linux utilities even on a non rooted Android). But their vendor lock in is second to none but Apple & MS.