The meat and potatos critique of Trotsky deals primarily with his theory of permanent revolution, which would have been next to impossible for the nascent socialist states to enact without having the full hammer of imperialism come crashing down with the combined might of every single imperialist, reactionary nation and their chickenshit puppets all at once. For the fledgeling Soviet republic, this would've been disastrous. They barely defeated the white armies and the token expeditionary forces of the imperialists; imagine what a full-on counter-attack would've looked like. Not to mention, Russia, having only very recently suffered the losses of WW1 being forced into yet another massive global conflict to establish socialism would've been idiotic. Finally, even if carried out with success, socialism relies on the will of the people to have any measure of success; imposition of socialism through violence and coersion is just imperialism with red flags.

Trotsky carries somewhat of a martyr-like reputation in the west as he was an obvious political opponent of Stalin, and with that, the Trots like to pursue the narrative that Trotsky should've been the actual successor to lead the USSR, carrying on the legacy and will of Lenin, instead of Stalin, the villainous cur that imposed a cult of personality and awful dictatorship, thus betraying the revolution. This is an ahistorical take on the USSR's succession of leadership, as Stalin did not just walk into the politburo one day and declare himself king of the USSR. However, this does serve to distance the trots from the "evils" of the USSR, creating a pointless dichotomy of trots=good commies; while USSR and, coincidentally, every non-western communist movement=bad commies.