Do you actually think the referendums were legitimate? In Crimea there likely was a majority who wanted to join Russia but even then the results were way higher than in previous polling. Plus Kherson and Kharkiv areas were and are not pro-Russian since the invasion and the referendums there were clearly falsified.
It’s not a simple ethnic conflict and the majority of Russian speakers in Ukraine do not want to secede to Russia and do not support the invasion. It is harder to tell in the Donbass because of a lack of data but it is still true that Russia orchestrated the removal of independent-minded leaders for puppets from 2014-2018 or so.