Sometimes people do plan things, although a lot of the stuff I mention was relatively spontaneous. But what sustains it isn't careful planning. It's most people going along with systems they don't understand, impulses they've never considered.

E.g., the impulse where they protect people like them and people familiar to them before people unfamiliar to them. That very rarely comes from a considered plan of "let's screw over black people". But that's often the effect.