Re: Who was it?
Forks succeed when the major contributors jump ship. The ones who are frustrated with existing process, or the owners.
OpenOffice was refusing decent patches left and right under Oracle stewardship and it pissed people off so much they forked and here we are. I should note it's not the first or last time this happened with Oracle - Hudson forked as Jenkins & MariaDB forked from MySQL. It seems they have a "reputation".
I bet the majority of people submitting to OpenOffice are Oracle employees and maybe some consultancy firms scraping by on support contracts. Basically bug fixing and maintenance mode.