I saw that this instance had a large number of users so I thought "more users->more content->more fun". Apparently, I had to prove my value by answering 3 questions that showed my interest in their community and my value as a potential future member.
What could possibly be my value to a general purpose instance besides money? I'm a software/cloud engineer so I guess there are things I could help with, but my guess is they were expecting me to say "I can donate".
I get it, they need donations to exist, but this upfront? And to a community I don't even know? Maybe I'm imagining things and they were looking for something else?
Do all instances rely on donations? I'd like to contribute to the instances I enjoy at some point. But only if I feel at home with them, not as a prerequisite to join.
What in this message made you think your rejection had anything to do with donations? Seems like you're jumping to that conclusion without any evidence.
The instance I joined had a boilerplate form asking why to rate-limit sign-ups. It said that almost all applicants would be approved, but this helped to control the growth. Got in with a very simple request that used humor related to the instance itself. I would expect this is similar in motivation.