>>685434He's just an easily memeable figure and a vast majority of self-identified leftists online get their understanding of marxism and history through passively absorbing memes (icepick, newspapers, etc).
There's also a modern dogmato-revisionist tendency that remains incapable of reckoning with the legacy of the USSR and retreated into a contradictory morass of haphazardly assembled positions basically designed to self-flatter and vicariously enjoy cheerleading for bourgeois states. For them a hatred of Trotsky remains a totem and cornerstone of their historical perspective.
Another reason is that today trotskyism is generally (and ahistorically) viewed as the most prominent communist tendency in the west and thereby somehow shoulders the blame for there not having been a revolution in the west. Besides trotskyism certainly never having been a substantial majority, and hardly existing as a cohesive tendency as such since the 'trotskyist movement' was really just a loose grouping of anti-stalinists of all sorts who rallied around the figure of trotsky and promptly fell apart after his death. Besides that, no other tendency has achieved anything meaningful in the west which is not the fault of some incorrect line but of a generally unfavourable epoch and historical conditions.
As for Trotsky himself, just read his works. Start with results and prospects, then his history of the october revolution, then a new course and the debates in the comintern, then a revolution betrayed.