Who Amazon does business with is their own decision.
But terminating Parler with such short notice that they had no chance of moving to an alternative without major disruption of their business. Well. That is deliberate destruction.
Without knowing anything about US civil law, I would expect Parler to have a strong case.
The suit states that Amazon and Parler had a contract which stated that 30 day notice would be given before service termination, and if that's true then this does seem like a strong suit.
But the entire text seems really biased and borderline crazy (all that stuff about monopoly/antitrust - since when is AWS even close to a monopoly?) so I wouldn't be surprised if they elided that the contract also allowed for early terminaiton if certain terms were being violated.
But terminating Parler with such short notice that they had no chance of moving to an alternative without major disruption of their business. Well. That is deliberate destruction.
Without knowing anything about US civil law, I would expect Parler to have a strong case.