The shortest explanation is that COVID changed customer demand, in both directions. And switching from one fab to another, even if they are the same process si

The shortest explanation is that COVID changed customer demand, in both directions. And switching from one fab to another, even if they are the same process size, requires significant work. This caused a scramble where customers found alternate paths to satisfy requirements. Buying up stock of other, similar chips (which now creates a shortage of chip "b"). Reserving time with a new fab. Or deciding not to have navigation in certain car models. Or halting sales for a while. All of which drives another cycle of churn into the schedule. This repeats itself over and over, like an earthquake with aftershocks, until things smooth out.