There is clearly no genocide.
From Putin himself:
"[The Donbass residents], who did not agree with the [2014] coup [in Kiev], were immediately hit with punitive military operations. A blockade was immediately put in place against these people. They were subjected to systematic shelling, air strikes. This is what is called 'genocide'".
https://sputniknews.com/20220318/putin-main-goal-of-russian-operation-in-ukraine-is-to-set-donbass-free-from-genocide-1093987300.html
This is a civil war, not a genocide. By the way, preventing a genocide is a legitimate reason to ask for an intervention of UN. This is not the path they chose.
On chemical weapons, it is clear today that they "do not exist" but at the time, they were "proof" from the CIA and the Italian secret service that they existed. They were all fake, however, they were several proofs. It was word against word. French for example said chemical weapons existed but there were no production and Iraq agreed to cooperate for their destruction so they were against war. In the end, some old and mostly unusable chemical weapons were found in Iraq. I think we agree on this issue, I just wanted to bring nuance on what you wrote.
They profit way more from Ukraine as a puppet state than as an allied of Europe.
Imperialism is not just a question of money.
You assume that Putin anticipated sanctions. He clearly anticipated some of them but not that much. He also thought that way more Ukrainian would support the invasion (like in Crimea) and that the Ukrainian army would be less prepared and so on. But it is a whole other debate.
They annexed Crimea in 2014. Do you really think that the annexion of a region from a sovereign state is not a clear sign of imperialism ? Furthermore, I find it much easier to believe that Putin wants to submits Ukraine to Russia (https://en.wikipedia.org/wiki/On_the_Historical_Unity_of_Russians_and_Ukrainians).