Former members of Red Guards, a Maoist cult with groups across the US have written a post-mortem of the high control group.
There are many similarities here to Black Hammer, another recent Maoist cult that turned fash. The first thing that sticks out is both groups obsession with fighting other leftists. Infighting was more effective for Red Guards than Black Hammer, who lost most of their left-wing support after their failed campaign against antifa.
This is worth a read to learn red flags for high control groups. No one is immune from falling into a high control group like this.