I think Ukraine could only have gotten away with this in the current situation where the US is detaching itself from supporting them, because if Russia genuinely thought that the US was behind taking out a large percentage of it's strategic nuclear fleet, the consequences of that are nightmarish to think about.

Those airplanes are one of the things that give Russia a second strike capability, and if they lose that capability, then they are going to be on a hair trigger in a nuclear crisis.