You seem angry about lack of funding. Why do you believe anyone is entitled to impose a paid-by-the-hour model over open source? How do you think the entire technology stack you’re typing this on was built?
If project goes down and maintainers leave the project, Microsoft also loses money spent on their engineers contributing there. They will have to fork the project, put more people on it, waste a lot of time by re-learning code and start contributing. Money and time would be better spent by just donating to current main maintainers.
Sunken cost fallacy refers to irrational decision making about a future action, incorrectly using the costs of past actions to do so.
It is not a fallacy to assess or reassess the value or effectiveness of past actions.