The Microsoft deal was originally negotiated by Gil Amelio, and while the monetary investment is what got the headlines and is what people remember, the most important part of the negotiations to Apple was that Microsoft committed to keep developing Microsoft Office for the Mac, which they had been threatening to cancel due to the platforms insignificance. Without Office, the Mac had no future.
Yeah that was a big part of it, but I wouldn't go so far as to call it more important than preventing immediate bankruptcy.
"We'll give you a wodge of cash and we'll keep supplying Office for Mac, so you can continue to supply the market with a rival to our OS at a volume that's insignificant to us, but just significant enough to prevent Windows from falling under the DoJ's definition of a monopoly".
