The circle around Ayn Rand became totally conformist because its members held that rationality was the only way to decide anything and that being rational meant agreeing with her.

Over time, they all come to share Ayn Rand's views and opinions on everything, from music to art, to clothes. She gets a dining room table and a bunch of them get the same dining room table, and it becomes incredibly conformist, because they've all believed they're acting rationally. And they believe that to act rationally is to agree with Ayn Rand and they believe there's no other way to make decisions than rationality. To disagree with her is to be irrational.