One way in which the new government in Kiev acted remarkably stupidly was to remove the right of regions to give Russian ( or other minority languages) official status. That was an invitation to people in Crimea especially to feel they were threatened.

Crimea was of course part of Russia for far longer than it has been in Ukraine - and until the break-up of the Soviet Union its transfer in 1954 without any consultation with the inhabitants was a trivial enough change.

I would suggest that until this crisis blew up pretty well everyone outside the two countries involved assumed that Crimea was Russian, insofar as they didn't mix it up with Korea, the way that many people in Britain tended to confuse the Falklands with the Shetlands when that one hit the headlines back in the 80s.

The most sensible way to resolve this would be for rapid elections to give the new government greater legitimacy, and for the law attacking the status of Russian and other minority languages to be reversed. And they need to get rid of antisemitic and near fascists from anywhere near government.

As for Crimea, it should be accepted that the people there should have the right to decide what country they live in. If a fresh referendum with international observers would help, that should be agreed by Russia, and allowed to take place, as a face-saving exercise. It is hardly possible that the result would be different.