Maybe AWS wants to preempt those lawsuits by just ridding themselves of the headache? Don't blame them. Amazon is not in the "hosting controversial content for shits and giggles" business.

Right now Section 230 means that Parler end users would be sued, not Amazon or even Parler. If Section 230 were repealed then Amazon would be open for lawsuits.

Lawyers usually aren't going to go too hard after Parler end users, most of them don't have much money. Amazon however is a different story.