CoMaps emerged because of a lack of transparency in Organic Maps amid concerns that the project funds were being misused. There was increasing worry that Organic Maps shareholders intended to sell or monetize the project like Maps.ME, which it originally split from.

https://openletter.earth/open-letter-to-organic-maps-shareholders-a0bf770c

CoMaps was created embracing FOSS principles, transparency, and community driven governance.

Lwn has a pretty solid overview:

https://lwn.net/Articles/1024387/

There are a lot of small things that played a role, so I don't think I'd be able to give a good shortened version.