Churchill included members from all three parties in his war cabinet.
Because they were all in favor of defending Britain.
Churchill appeased the opposition with three cabinet appointees - Halifax, Chamberlain, Beaverton. But it was window dressing. He had enough support to any desires to appease Hitler. Halifax got no change from Churchill and Churchill sidelined him by sending him to the U.S. Churchill converted Chamberlain, but no matter, Chamberlain’s illness sidelined him anyway. Beaverton had his differences with Churchill but he was not one pushing for appeasement with Germany.
1. Regardless there were not elections at the time in war torn U.K.
2. The exact situations are not analogous. There are enough differences between the U.K. at war in WWII and Ukraine defending itself now, that one cannot say the circumstances are equal.