The moment you give away something for free people value it at $0 and expect you to support it for free indefinitely. They get angry immediately if you decide to charge money for it, as if it was some incredibly smart and prudent decision to build your project/business on an external dependency you made zero effort in keeping alive.

No wonder then that he decided to quit the open sourcing but keeps working on it for money.

I still don't get how people see these 100% voluntary projects, which by definition are always a donation of free labor, and then get angry when the donations stop. All software projects have life spans, the difference is that anyone can go and keep maintaining an open source project to extend the lifespan

While I am personally guilty of free loading on a lot of open source projects and never giving anything back while profiting myself, I was never under the illusion that I am owed an endless stream of free code and maintenance. If the underlying project is discontinued it is on me to either keep maintaining it or switching away from it. This is true even in banal situations like with software that is still being maintained and you're merely sticking with a fork of an older version.