>Why are they developing so many different mobile OS platforms at the same company ?

As the title say , Google is just investing in it. They don't develop the codebase of the OS.

They want to push their free services to collect data , it's their business model after all.

Also it's designed for emerging market , KaiOS phone don't have touch screen, they are supposed to be super lightweight, as a matter of fact they already have a billion users which I personally found to be insane for a startup I've never heard of.