The ramifications of MS taking two of Amazon's biggest cloud clients away is actually a very interesting point. Like
@Old Gamer said I'm sure regulators have been considered that, but like you also said I doubt most of the people vehemently pushing for the deal to go through in online debates ever once consider that side of things.
When you think about it, it significantly reduces whatever presence in gaming Amazon already had, in one fell swoop. That plus I've seen statements in the past that when game companies had the chance to renew on cloud providers, they picked AWS or Google over Azure. So in just buying said companies, MS essentially locks them down to Azure because there's no what they're going to own them and yet let these same companies use anything but Azure for their cloud infrastructure.