Tip which scales? You seem to be under the misapprehension that there was serious internal pressure for Brendan to resign. There was not.
The problem, of course, is convincing you of that. I can point you to https://blog.mozilla.org/blog/2014/04/05/faq-on-ceo-resignat... but of course you can decide to not believe that. I can also tell you that I'm a Mozilla employee (that's a clear matter of public record anyway) so I have some idea what was going on internally, but you don't have to believe me on that either...
> a lot of Mozilla employees were upset by the Prop 8 thing
A lot were. There's a difference between being upset and wanting Brendan to step down, though. So you get posts like http://subfictional.com/2014/03/24/on-brendan-eich-as-ceo-of... and http://www.twobraids.com/2014/04/back-into-light.html and http://incisive.nu/2014/thinking-about-mozilla/ which seem to me like the polar opposite of "politicizing Mozilla".
> but I haven't seen any factual numbers
Dare I say that this is because there aren't any? But "Employees support their new CEO in spite of disagreeing with him on some political issues" makes a much worse story than "Employees revolt against new CEO", so the press ran with the latter, facts be damned.