I don't know why people think AGPL changes anything here. The very first of this wave of moves to non-FOSS licenses, and the creation of the SSPL license we are discussing here, was Mongo moving
away from the AGPL.
What these companies want is licenses which prevent AWS and other cloud providers from competing with them on their specific technology, regardless of how much those same companies are contributing to the technology. Redis is the most extreme example here - by all accounts I've read, Amazon was a major contributor, not just throwing bug fixes here or there. But that doesn't help Redis Labs, they want money, not code. And the AGPL would have done less than nothing to help stop Amazon from running their own Redis service: Amazon was already doing everything (or at least most things) that the AGPL would have required of them.
SSPL is just a figleaf. No one sane redistributes third party SSPL code without having a contract with the company, it's essentially proprietary in all but name. But it allows the company to maintain this air of open source legitimacy.