Afaik, LibreOffice was a fork of OpenOffice because OpenOffice refused to implement quality of life features in a timely manner.

https://en.m.wikipedia.org/wiki/OpenOffice.org#LibreOffice

Apparently there was also some footdragging by Sun (because Sun) and later Oracle (because evil) about creating a neutral caretaker foundation to guide development.

Circa 2010/11, the development community decided to do it themselves.