Software, especially open-source has an over-representation of people that identify as LGBTQ. Brendan openly signaled that he thought a good subset of his employees did not deserve the same rights as others. I don't see how he could have been an effective CEO after doing that.

It would've been a huge liability for Mozilla. An employer is not allowed to discriminate on sexuality. Fire any LGBTQ employee, and there's now a decent chance that Mozilla will now have to prove in court that it didn't have anything to do with the CEO openly hating gay people and creating a hostile work environment.