Just my recollections on the Bungie acquisition, speaking as someone who was obsessed with the studio. I certainly had felt heartbroken/betrayed at the time, but what can I say? I was a teenager.
When Halo was announced at MWNY, Jason Jones (who today is the last original Bungie member) finally gave fans a peek at their codenamed "Blam" project, officially announced the title as Halo, and said that it would be out "first" for the Mac, though it was implied that a simultaneous release alongside a Windows version was likely. The hybrid release was expected, as they had done the same with Myth 1 and 2 as well as Oni.
Later, after the buyout, the internet seethed with rage. Now, according to this revelation, we know that Steve Jobs raged, too. What was announced initially as "Mac first" now looked like it would not see the Mac at all, and the best game developer for the Mac was now Xbox-exclusive. If you ask me, what angered Steve was not the prospect of damaged sales. From everything that I've heard about him, it is more likely that what upset him was that by Microsoft buying Bungie, it made Steve into a "liar." It is easy to imagine him thinking of his keynotes as his "promises" to the community. In short, he probably felt humiliated.
On why Bungie "sold out" in the first place:
As was mentioned, back then they really had to survive on a game-by-game basis. Bungie had recently expanded and created a new studio, Bungie West, to work on Oni. Bungie had finished Myth 2, and was concentrating on "Blam" (later revealed as Halo). Oni saw delays, features were cut, there were more delays, and I believe sales ended up being lackluster. This incurred a large financial hit that put them in jeopardy, and it was unlikely they would have survived to finish Halo. Then Microsoft offered them a solution, and they took it.
Halo became Xbox exclusive (though was later ported to the Mac by Gearbox Software, to appease PC and Mac gamers as hinted), and if I recall correctly the rights to the Myth and Oni franchises were sold to Take 2 (who released a subpar Myth 3 developed/rushed by Mumbo Jumbo).
At least that's the history as well as I can remember it.