While I loath the moves to closed source you also can't fault them the hyperscalers just outcompete them with their own software.
An alternative I've seen is "the code is proprietary for 1 year after it was written, after that it's MIT/GPL/etc.", which keeps the code entirely free(ish) but still prevents many businesses from getting rich off your product and leaving you in the dust.
You could also go for AGPL, which is to companies like Google like garlic is to vampires. That would hurt any open core style business you might want to build out of your project though, unless you don't accept external contributions.
Also, I'm not sure how anathema AGPL is. It's true I rarely see AGPL projects being hosted by big clouds, but AGPL is also just less popular as a license. I know AWS hosts AGPL Grafana, but iirc, they had to work out some deal with upstream.
2. You're forgetting bureaucracy and general big company overhead. Hyperscalers have tried to kill a lot of smaller external stuff and frequently they end up their own chat apps, instead.