looks like rendering adblockers extensions obsolete with manifest-v3 was not enough so now they try to implement DRM into the browser giving the ability to any website to refuse traffic to you if you don't run a complaint browser ( cough...firefox )
here is an article in hacker news since i'm sure they can explain this to you better than i.
and also some github docs
Most likely different incentives and platform culture.
Customization isn’t that big on iOS, other than the occasional viral fad, so there’s less interest for custom keyboards and in return less development spent on it.
Monetization of custom keyboards is also really hard and due to limitations on tracking and collecting data the incentives that Android has don’t really exists on iOS.
So what you end up with is a handful of custom keyboards often by big players that have bags of money to throw at it or as a companion to a regular app (e.g. Grammarly, GIF apps) to fulfill a specific function.