Thinks about it:
-collectivisation and rapid industrialization: all policies Trotsky supported, he even said Stalin copied them from him
-anti-bureaucracy: Stalin fought the bureaucracy of the party and state in the great purge so much so that the bureaucrats where still butthurt years later and denounced him in 1956, after his death
-permanent revolution: Stalin literally spread the revolution to half of Europe and supported Mao by giving him manchuria and captured Japanese weapons, socialism in one country was a complete meme after ww2
Why did they hate each other so much?