I believe that the death blow which lead to the fork LibreOffice was the lack of trust in Oracle commitment to Open Office and open source in general, after Oracle acquired Sun Microsystems.
Sun indeed had largely reduced its involvement in the project in the last years, and there was the "Symphony incident" [1]. The death blow was when Oracle arrived, started the trial with Google over Java/Android, inherited MySQL and almost killed it, inherited OpenOffice and the future did not look bright anymore [2, in German]
[1] https://web.archive.org/web/20130927072255/https://lwn.net/A...
[2] https://web.archive.org/web/20131024094250/http://www.heise....