I'm not sure I want that kind of "conglomeration" in the FOSS space. Sure, there can be benefits to having a behemoth with a lot of resources behind it to support FOSS projects. But it also brings with it various problems of incentives and resource allocation. Managing multiple different software projects within one organisation is something a lot of well-run, for-profit companies struggle to do effectively, I don't think Mozilla would be much better at it.

Also, I personally don't have any issue with Mozilla but a lot of people seem to hate them. I can only imagine all the internet drama that would ensue if they started acquiring projects like LibreOffice and Nextcloud.