[benologist]

The most likely way it happened was a multitude of complaints received in workers-rights or competition institutions because that's a formal way to complain about companies doing unfair stuff, and when Amazon abuses their workforce or vendors it affects a LOT of people with the right to turn to these institutions. These institutions will default to having paperwork supporting their process and decisions as they routinely need to use the legal system to solve problems. I think it is very unlikely a competitor could orchestrate these consequences for Amazon's actions.