Trosky was just a much better, smarter leader than Stalin who would have put the Soviet Union in a much better position. A USSR under him wouldn't have had a Hitler at the gates of Moscow or mass famines with vast lands with the best soil quality in the world. I'm not a Communist or Marxist so I don't give a fuck about how he failed this or that marxoid purity test or "theory" nor a /pol/tard who seethes at him being Jewish

Stalin was a shit military leader. He ignored mountains of evidence for Barbarossa and had a German deserter shot who warned of it. Before WW2 he killed or sent to gulags any general who believed in deep operations instead of ideologically-motivated but tactically retarded "proletarian" counter attacks like Rokossovsky and instead put in charge Budyonny who thought tanks were worthless compared to cavalry, banned mechanized divisions, thought laying mines was for cowards, and would later cause the biggest encirclement in military history. These purges led to Russia getting manhandled by Finland. He also ruined the Polish-Soviet war by opening a new front instead of diverting his troops to reinforce Warsaw

In The Revolution Betrayed, Trotsky predicts the damage Stalinism would do including the economic and bureaucratic stagnation of the USSR and how it would continue to get worse once Stalin was gone, eventually leading to its eventual collapse, as well as the problems with dekulakization

Mass industrialization was basically the only major thing Stalin managed to do right and ultimately a saving grace, but he copied that policy entirely from Trotsky and the Left Opposition

Almost every one of Stalin's decisions was catastrophic and would've sank any country that didn't have all that land, population, capitalist support, and an enabler like FDR. The only good things about him were that he could rally the people and was likeable unlike Trotsky, who was an asshole, and stopped the autistic crusade against religion and "Russian chauvinism".