You're referring to the votes to join the RF that happened after the territories already voted to secede from Ukraine, right? Majority ethnic Russian areas voting to join Russia after being attacked for years by openly Nazi-identifying Ukrainian military units, voting to secede, and requesting Russian military assistance to protect their sovereignty and right to self-determination doesn't seem like that much of a stretch to me. I'm sure there were some people living there that would have preferred to continue watching their neighbors get murdered by men wearing swastikas, but I don't have any trouble believing the vote wasn't close. I'm no UN election observer, but if you asked me which outcome was more likely to be representative of a general democratic will of the majority of residents between that and say, any US presidential election in my lifetime, I don't have any question about which I'd pick.

The Ukrainians that don't want to "give up territory" aren't the Ukrainians that actually live in the territory in question: they're the Ukrainians that wanted to continue killing the Ukrainians that lived in those territories for not being "Ukrainian" (i.e. White) enough.