Mozila is not a political organization but someone in a position of power took an action that hurt some big donors. Those donors are well withing their right to stop donating after that.

But since they believe in the foundation mission, despite the actions from the leadership, they looked for an compromise that Eich accepted (apologizing) and then refused to fulfill his end (the real big problem).

At this point there was no more compromise, either Eich is out or the donors are and Mozilla does not have the luxury of losing donors, most of their money may come from Google but for then every penny counts.

This was not political activism by Mozilla, it was choosing between a rock and a hard place, either losing a big chunk of money or loosing the CEO and making some irrelevant people unhappy, the best decision is very clear to me, CEO is easy to find a replacement, money not so much and 99% of the people complaining are not either.

This was political activism by the donors and they are totally within their right to do it with their money.