So, it's partially just a bit. Many Trotskyists are true comrades in day to day action, Online ones like Steven Brust are super cool, and I'm friends with many of them. Don't let the online shit break left unity.

Also many Trot orgs do practice demcent. And many kept the left alive when there was nothing else extant as a revolutionary party. Those "Old Trots" were all alone in the early 90s as ML and Maoist parties were in chaos, save the few Anarchists that avoided the weird centrist insurrectionism that developed.

That Said...

Basically, in the Anglosphere just pre and post-WW2 the ML parties and Anarchists were smacked down pretty hard, while the Trots were seen as a safety valve for leftist agitation by the authorities and a way to prevent Soviet influence.

This allowed them to become the centre of the "New Left" in many ways. Unfortunately a combination of Trotsky being butthurt and actual semi-valid criticism of Soviet Bureaucracy coupled with the fact many of them were taking spook dollars from the start (which many rationalised as being sold the rope to hang the capitalists) meant that splits, weird political positions like supporting Fascists and Absolute Monarchs against AES, and general uselessness were rife.

This was especially pronounced in the UK where most major left orgs were Trotskyist and there was a major attempt at Labour Party entryism. It failed spectacularly for a variety of reasons including huge infighting, distracted from building a revolutionary workers movement at a time when labour militancy was at its peak, and was widely regarded as a bad idea that let Thatcher and Blair in.

A combination of these is why the stereotype of a Trot party is 30 people at a climate protest with a newspaper denouncing the 30 people they just split from, and supporting "Anti-Imperialist" Turkish Militia against the "Bourgeois Social Reactionaries" of Rojava.