I started organising in horizontal orgs and that didn't go very well and I observed a lot of inherent problems with constantly trying to avoid "hierarchy" as an end in itself. That was the fundamental shift that over the course of a year or two lead me to Marxist-Leninism, because then I joined a more centralised org and started doing political education around anti-imperialism. The crisis of the pandemic, the supression of the Bernie campaign by the Democratic party, and the BLM protests also showed me the limits of the politics I had up until that point.