Crimea held their referendum in 2014 and requested Russia absorb them. That was 8 years ago. If that vote were bogus, we would have heard of widespread resistance sabotage since then.
I have heard nothing.
The best answer for why is the vote was correct and the vast majority prefer Russia.
Looking at the maps of Russian language prominence, Kherson is less overwhelming than the other oblasts. If there are going to be folks who do not prefer Russia, it would be there, and I think the referendum vote there did show lower numbers than the other 3 regions. Something like 75% vs 90+%.
Please refrain from using facts. You are expected to react with emotion here.