I know nothing of this person or Mozilla internals, but I could imagine a company heading towards bankruptcy, that was avoided while still losing market-share. In this situation the role of CEO could become more important as market-share decreases and the situation becomes more precarious.

Now if that person caused the downward slide to begin with, that's a different conversation. Again, I don't know the internals of Mozilla well enough to make an educated argument one way or the other.