Yes and when refusing service Amazon would not be fulfilling their part of the contract. Negotiations would be harder for them in that case.

Cutting service is the very last cudgel to come out for large contracts. And only when counterparty's insolvency is looming. Which may or may not be the case for Twitter.

If Amazon concluded Twitter's insolvency was near it would certainly negotiate on the contract. Before cutting service. Which is why it's interesting to watch Amazon's reaction here.