Brendan Eich was an odd case. He had views which weren't pleasant, for instance, he was against same sex marriage (dunno what he thinks of it now).
After Mozilla ousted him though, they largely became irrelevant (through mismanagement) and never recovered.
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So, I guess that while he might not be that pleasant as a person (there have been quite a few jerk CEOs in the sector), he is competent.
And maybe it is a legacy of that, but I also found that Mozilla spent too much in the way of resources on getting involved in random social causes, and they weren't even good at getting involved in those.
Like questioning YouTube.
To be fair, some of it might be that Google has a lot more money, but it is also on them for not utilizing their resources effectively (or until it was too late).