Conversely, why not invade to destabilize the incumbency of the non-stooge so that the stooge wins re-election and then use the stooge to negotiate a favorable frozen conflict? Or why even attribute it to POTUS at all? Why not attribute it to the fact that Ukraine's military power was growing due to the Western training that they were receiving over the previous 10 years, and Putin was effectively on a clock to invade? Eastern European conflicts have never revolved around who is POTUS.