During WWII, the West sent thousands of tons of supplies to the USSR. Without these the Nazis probably would have conquered them. We could have just let the USSR fall, but then we would have been faced with an even harder task in defeating Hitler, if it would have even been possible all. Ultimately, the West decided that given a choice between Nazi Germany and Communist Russia, the latter was the lesser of two evils.

If the choice now is between supporting Ukraine, even though they have some Neo-Nazis in their army, versus letting Putin's Russia overrun them, I'll take the former, and it's not even close.