If he thought he couldn't make any money implementing it, that means he didn't think there was a market for it that would return the investment. I think it's entirely possible he created that market by driving adoption until the point where that feature it could be supported.
The question can essentially be flipped, and you can ask why Intel didn't create the hardware with those features initially. The answer is likely that it would have taken more research (if it didn't already exist in much more expensive processors) and would have driven the cost of the processors to the point of not being worthwhile. Is Intel then responsible for setting the industry back by years, because they didn't market a processor they likely could if they took longer and/or charged more?
> The Intel guys offered not only to fully fund the development, but to fully staff it and pay Microsoft for all the bother.
In a world where increasing software complexity or having outsiders contribute a sizable or complex piece of code to your private codebase has no cost in future development complexity or runtime, this might have been purely an upside. In the real world, there's there are other considerations, which is likely why it was rejected. Otherwise, why would anyone turn down free development time? Are we to assume Gates was so capricious as to turn down something this beneficial, or that he had resons we haven't adequately covered yet?
> If someone wants to philosophically believe in rational markets and insightful and honest executives, well, that is a choice they can make.
I don't believe in entirely rational markets and honest and insightful executives, but I do believe in people following what they think that market will do, and in executives that turn down things they think are a bad idea, right or wrong. I'm willing to bet Gates had a lot more information than we do when making this decision, and had his reasons. I think it's possible that he could have been right.
1: https://en.wikipedia.org/wiki/Protected_mode#Operating_syste...