1. All three had to ramp up the vaccine production fast.
2. Moderna at least had problems with a Spanish production (contractor?) facility. In Japan they found pieces of metal and a lot of vaccines were trashed.
3. All kinds of weird crap (mostly junk) have been found from all three vaccines under electron microscope.

Conclusion: All three had serious QC problems and knew about them. Instead of abandoning the expensive but corrupted "hot" lots they redistributed them wide, far and slowly so it would more difficult to detect. It was a race to win TENS of BILLIONS of dollars after all so they all just got even greedier and nastier than usual.

Pfizer has paid fines over $5 billion since 2000 for all kinds of criminal violations in the US. Moderna was another Theranos in the makings with not even one product of their own before the Covid vaccine. It was do or die moment for them. So they were already dirty fuckers.

The other possible explanation is the "Evil Moriarty". Some super evil genius working through all three companies secretly but that would be something very very improbable.