It wouldn't matter for the anti-trust lawsuit, since they're alleging that Amazon conspired with Twitter to kick off Parler because Parler would steal Twitter's market share. (Well, trying to allege, because they don't even manage to allege that any further than "Amazon hosts Twitter" and implying there's no other reason Amazon would kick Parler off, despite spending half the brief complaining that they're being kicked off for being conservative.)
This seems like a good guess
But wouldn't that be easily thrown out / defeated if they weren't consuming those resources on AWS? Which seems easy to prove in court...
That didn't stop any of the election lawsuits.
Yes it did, they stopped. They started, were clearly bullshit, and then died in the courts - exactly as the system intended.