There are many options between incompetence and being actually 'in bed with', which I read to mean 'knowingly cooperating with', the criminals.

The first example is that it's simply more profitable for them to turn a blind eye unless one of the relationships becomes a public problem. They wouldn't be actively aiding and abetting the crime, but neither are they stepping up to ensure that it isn't happening on their systems. It's being complicit several steps beyond incompetence, but not the same level as active cooperation.

And, considering that Amazon has no shortage whatsoever of funds and skilled people to prioritize anything they want to prioritize, I'd say more than sufficient time has passed that they're at least at something resembling this sort of willfully ignorant stage.