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?
Honestly, you shouldn't.
Theoretically, Apple + Google take a % of all payments that go through their store, with the expressed reason being to "monitor and police the safety of the apps on the app store". You really should be able to trust apps on the official app stores, but I don't trust Apple or Google, so the whole system is moot I guess