The problem is that "cosmic-expansion" is the most natural choice, and that is already set as a synonym for space-expansion. From searching, my impression is that moderator intervention is required to undo a synonym.

@KyleKanos It was last year. I am happy that the new edit is approved! Still interested in the tag/synonym swap, which I am not sure it is possible to propose.

@KyleKanos As noted in the post, "I am aware that I can submit an edit to the tag info without posting a meta thread about it. I did, and the edit was rejected." It seems the change is controversial enough to warrant a meta post... (Also, do you know how to propose swapping synonym with canonical tag?)

By the way, once you have 3000 reputation you'll have access to close votes, which doesn't just mean you can vote to close, but it also means you can see how many people have already voted to close (so you can decide not to start an answer). Not an excuse for the way things are, just a note that things will be less annoying for you eventually.

I think the intended approach is that you, the answerer, will then edit the question to make it acceptable. This assumes the question was unacceptable in the first place and that it's clear how to make it acceptable...

"I assumed knowledgeable high rep users would either downvote the terrible answers [...] but they did not." -- not really how the site works, unfortunately; people who are knowledgeable about a particular topic are vastly outnumbered by those who are not.