At companies like Google, Microsoft, and Apple, you can work on a browser regardless of your political views. At Mozilla, you need to think a certain way first. A smaller pool of technical talent to choose from leads to worse technical leadership. Recall that Eich only became the CEO (over the opposition of a portion of the board) after months where Mozilla was searching and couldn't find anybody better. It's not that the people who have particular political views are particularly talented, it's just that some of them are talented, just like the people who disagree with them. If you can include talented people of all stripes, you can do better than if you restrict yourself to talented people from a single ideological group.