> there's the fact that AWS doesn't host Twitter's feed
This is funny (as in, LOL funny) to point out because it makes parler seem completely inept, but it's only technically correct.
They just negotiated a fat contract to host twitter, and that's set to go live in the next few months. Can that really not be considered an endorsement of twitter's content with respect to AWS' ToS? It's not like twitter just signed up for an AWS account like the rest of us do. There was a bidding and negotiation process. Sales teams on both sides worked on that contract. I don't think it's so unreasonable to take the existence of that contract as evidence that AWS reviewed twitter's content and deemed it acceptable content.
Why does this matter? Legally, I don't think it does. I don't see any good reason why AWS shouldn't be allowed to selectively enforce their ToS.
But Parler sought to compete directly with twitter. At the time of account termination, they were growing at a rate of hundreds of thousands, maybe millions of users per day, and in a way where it's not hard to imagine it being zero-sum (twitter users terminating their accounts and going to parler).
I don't think the case would succeed, but I do think that parler can make an interesting case about AWS picking a winner and damaging a loser.