I thought Trotsky was the international which is why Stalin had him assassinated’
Ever heard of the Comintern?
From what I have read the differences that Trotsky and Stalin were their visions of what collectivism was supposed to be. Trotsky looked at it with a more Jewish idealism while Stalin did not.
Stalin himself was an anti-Semite (surprise!) which just added more fuel to the fire. He was planning his own pogrom/Holocaust within Soviet borders to get rid of Jews there but while he was on vacation his doctor slipped him a mickey that caused him to die.
This is known today as the Little Purim because Stalin died on the Jewish holiday of Purim. Read the story of Purim and you’ll understand his death better.