LibreMobileOS (LMODroid) – Rich Featured Privacy Focused Mobile OS Based on AOSP

I like some of the features, but the website doesn't tell me why I should trust them, or directions on how to build the OS from the source code for people who have never done something like that, like me (not that I'd be able to audit it anyway).

With GrapheneOS, enough people have their eyes on it, that I can trust it without reviewing all of the source code and compiling it myself.

After looking what alternative mobile OSs lately, there seem to be a few around. The ones that have appealed to me so far are Ubuntu Touch, Mobian and FuriOS. I see there will be a Ubuntu based version here soon. What I can’t understand though, is why don’t these really clever people work together on fewer solutions with similar end goals? Is it that it’s difficult to manage opinions and decisions? Or that people don’t check the market before developing alternatives? Or something else?