What happens? Are you asking what the government would do if Amazon gains a monopoly and abuses that power?
If so, there are lots of possibilities, including the break of Amazon into baby-Amazons like AT&T in 1984 or Standard Oil in 1911. They could install overseers like they did when Microsoft was found guilty of abusing their monopoly. It wouldn't be an unprecedented situation.
You’re missing the point. If a monopoly is created because of government regulation and no competition can thrive because of government policy. There is no monopoly abuse. It’s just how it is because the government screwed up.
So what was different with AT&T? You couldn't just create a phone company and compete with AT&T. They had franchise agreements with cities and exclusive rights for space on telephone poles.
They were still found to be an abusive monopoly even though their monopoly was created by government regulation.
If so, there are lots of possibilities, including the break of Amazon into baby-Amazons like AT&T in 1984 or Standard Oil in 1911. They could install overseers like they did when Microsoft was found guilty of abusing their monopoly. It wouldn't be an unprecedented situation.