I doubt those were particularly profitable, but there was a lot of innovation back then.
Moreover, why risk installing a 3rd-party keyboard app when the App Store is filled with adware and malware? All those handy flashlight and camera apps are a Trojan's Horse, why should one assume that the various keyboard apps in the App Store aren't keyloggers trying to steal my login info?
In 2025 I can do mostly error-free blind typing on the Pixel 7 keyboard, with all autocorrect and predictive spelling intentionally turned off. Why would I need innovation?
And unless the app gets acquired by the big companies, it will eventually turn into malware.