Obviously you're referring to Brendan Eich. But you're wrong: Eich was not fired, and he was not forced to resign. In fact just the opposite: the board tried to get him to stay. This should not be news to you: it was in the FAQ on CEO resignation, from April 2014 when it happened:
https://blog.mozilla.org/blog/2014/04/05/faq-on-ceo-resignat...
Q: Was Brendan Eich fired?
A: No, Brendan Eich resigned. Brendan himself said:
“I have decided to resign as CEO effective April 3rd, and leave Mozilla. Our mission is bigger than any one of us, and under the present circumstances, I cannot be an effective leader. I will be taking time before I decide what to do next.”
Brendan Eich also blogged on this topic.
Q: Was Brendan Eich asked to resign by the Board?
A: No. It was Brendan’s idea to resign, and in fact, once he submitted his resignation, Board members tried to get Brendan to stay at Mozilla in another C-level role.