I don’t know anything about Trotsky. But I do recall my Sophomore history teacher describing him as not a leftist by Russian standards was more of a anarchist.
Stalin = national communism
Trotsky = international communism
Trotsky was among the many victims of Stalin’s purges. But that doesn’t make him innocent. He advocated the violent overthrow of free societies such as the US.
The tactics of Trotskyites are different than those of Stalinists. Gramsci, Adorno, and Horkheimer would have allied themselves with Trotsky, and rejected Stalin.
Saul Alinsky was in the Trotskyite tradition.