This omits one of the most interesting parts of the story, which is how Firefox evolved as an offshoot from Mozilla in the first place.
Neither Fx nor Tb were part of the app suite--they were both offshoots that, at the time, really violated what the project was aiming for. The story of how Firefox came to be and roguish it was seen within the organization at the time is interesting.
I would love to read a real oral history of Firefox someday.