You have the Tatar Exile during WWII, people re-settling the area, and then later Crimea was borderline on being independent or part of Ukraine during the dissolution.
So you end up with the fact that, whether right or wrong, Crimea is full of ethnic Russians who were lukewarm about being part of Ukraine in the first place. So as sketchy as the whole annexation was, was it wrong? I honestly can't say it is, which is probably why Russia felt they were able to take that chance.
As a Russian who generally thinks that both Russia and NATO need to back down from the pissing contests they engage in...
Yes, it was wrong. Ukraine was done wrong by it. It was not done legally. Even if it was done with respect to the doctrine of self-determinism (I generally approve of secessionist movements), it was not done correctly. There are correct means of going about secession, and the War in Donbass was not one of them. It was a thin pretense for other geopolitical ambitions.
https://en.wikipedia.org/wiki/Marcher_Lord
(What I wonder is how Baskov's marriage had been supposed to take place in Grozny a few years back. On the equation svadba==vodka, my best guess is that although the sale of alcohol is heavily controlled in the Chechen Republic, the consumption of alcohol, at a private party, would not have been.)
Also related: https://news.ycombinator.com/item?id=23914667
[1] from time to time I've seen Kadyrov invoke the spectre of foreign separatist influences. Given his paternity and history, a wild guess from the outside is that he'd likely know about such things, from back when the influences were on his side.