Apparently, in the case of Parler, believing that you should allow users to post any legal content without moderation. (I know they didn't lose their domain, but the effect of being denied hosting is functionally the same.)
Parler was removed for being under-moderated, sure, but with that aside, it was also a huge censorship platform.
https://www.independent.co.uk/life-style/gadgets-and-tech/pa...
https://www.techdirt.com/articles/20200627/23551144803/as-pr...
Regardless, they signed a contract detailing what they could and could not host on aws. They broke it. Its not like they were unaware of the requirements. Moral of the story, if you promise X, dont promise someone else Y if X and Y conflict. You are going to be breaking your word ine way or another.
No, it wa, IIRC, that Parler wasn't meeting obligations under the ToS for dealing with content prohibited under the ToS when they were notified of that content, and were failing to do so for an extended period of time demonstrating either persistent unwillingness or fundamental incapacity to fulfill their obligations.
Some of the content banned by the ToSay may also have been illegal, but that wasn't the issue, and neither was the simple fact of hosting the problem content.
They just didn't. There's a difference between being slow and just not doing it at all.
https://www.techradar.com/news/twitter-signs-up-aws-for-its-...
Regardless, from the sound of it Twitter was working with Amazon on this integration. This means Amazon knew Twitter was at least planning on migrating. If Amazon was serious about being consistent they should have told Twitter right there and then that they would not be allowed on AWS since they violate AWS' terms of services in the same way Parler does.