As both you and MeganC claim, though neither you have proof of that being the reality. However, had that become the reality then there would have been united support for getting involved including Western Europe. Don't even bother to bring in Neville Chamberlain.
Because it was worth the attempt, even though it failed.
It was then fully understood that, in that case appeasement was just that. However, Hitler had already shown his propensity to take military action, even if the claim was accurate that the majority of the inhabitants were German peoples.
But as it stands now, it is just the two of you, and most likely the rest of the Zeepers, opinion as well. But opinions are not reality. So, it would have been worth finding out what the reality would have been. Instead, we are involved entirely based upon conjecture & opinion. In addition, we would have had undisputed truth that Russia had broken the tenets of the peace agreement.
Yanukovich did a 180 degree u-turn regarding participation in the EU, and instead tried to ink an agreement with Moscow instead, which is what set off the Maidan revolution. Then he flees to....Moscow! What more do you want?????
Your lawyerly arguments are irrelevant. We aren't dealing with honorable people here, we're dealing with Russians. I've got books full of evidence of Russian perfidy in Ukraine prior to and after 2014 in my library, written by respectable historians. Not your colleagues' anonymous yewtoob videos. Well researched and densely footnoted. Online timelines published by news organizations like BBC from 2014 bear them out.
Or shall we talk about a REAL coup attempt from 2014, led by one O. Bahtiyarov, complete with Molotov cocktails, intending to overthrow the interim government left in place after Yanukovich fled. Funded by a Russian entity calling itself the "Eurasian Youth Union'. Much more recently, Ukraine disrupted a plot to assassinate Zelensky.
How much more subversive do Russians have to be before you'll recognize it?