Did people become billionaires at those companies before or after they started being enshittified?

The exact threshold doesn't matter. What matters is that the companies shift away from "make something people want", which is what PG says justifies the money that's made.

The timing doesn't matter because monopoly -> enshittification was always the plan. Hence FAANG were valued with the expectation that they could turn the profit knob at the right time.