Mozilla itself deserves to shoulder at least as much of the blame due to a number of decisions that range from mediocre to downright terrible. And I'm not even talking about what happened with Brendan. I'm talking about the organization's downturn during the years that directly correspond with the tenure of people like Gary "JavaScript rendering engine" Kovacs and the years that saw Sullivan at the height of his influence.
The engineers aren't blameless either, having allowed themselves and the engineering culture to become the target of whatever neutering that did occur. "But I mean, these are business people; this kind of stuff is what they should know, right?" Sure, right. Totally let 'em go ahead and pursue those useless fucking partnerships at the costs they're coming with. After all, that's what real businesses look like.