> we would've bent over backwards to make sure everyone was happy
Or maybe you wouldn't. I guess it all depends. If you happened to decide the BBC's goals were becoming contradictory to your own then who knows which way you'd bend? The point is YOU would be in a position to say yes or no to their needs, and no offense but to tell a very large company like the BBC, "trust me, I'll make sure you're happy, now build all your web pages on top of my library" is not particularly reassuring.
And I don't think anyone has to be a mindreader to know what you'd say if they submitted a patch that meant you'd have to lose some of the selectors you now support and run more slowly in order to add support for a browser with 1.5% market share.
They looked into it and determined it wasn't cost effective to maintain a parallel fork. Okay, whatever. Their needs are unique and they came up with a unique solution, so what? This isn't a zero sum game.
> C'est la vie.
Indeed. For organizations that don't have to give full support to the same minority browsers that the BBC does, then of course it makes sense to use an off-the-shelf library like JQuery. No one ever suggested otherwise.