According to Amazon's response to Parler's lawsuit, they were warned for months about their content.
https://www.courtlistener.com/recap/gov.uscourts.wawd.294664...
There is a handy summary of this on Ars Technica as well. That article also says Parler was relying on volunteer moderation to clear their backlog of over 26000 posts.
You wrote that Amazon warned Parler about their content, but that's not what your link shows. It shows that Amazon asked a question about policies regarding specific posts, and Parler answered with their policies.
Also note that it wasn't removed. I'm not even going to repeat that post here, but absolutely no platform would keep this online if reported, so "very similar terms of service to other content companies" as someone up this thread claimed isn't exactly true.
https://www.gadgetsnow.com/tech-news/read-amazons-letter-to-...
Or they were completely hands off? Which is it? Goalpost one or two?