Ah, I see. I wasn't clear. Let me try this:
I don't think Ms Gates knew anything about computers and I don't think IBM would have picked MS-DOS over a technically superior OS. I think 3 things happened:
1) Mary mentions to John the chairman of IBM that her son has a company doing "Computer Stuff" (they were the premier BASIC on CP/M at the time, IBM was planning to have BASIC in ROM so would have been talking to Microsoft about that). John asks the team doing the PC if this "micro-soft" has an OS like CP/M or if they are just a language company.
2) The question gets back to Bill who scrambles to say "Sure we can do OSes too! we have this thing we're calling it, uh, "microsoft disk operating system" MS-DOS for short. (while they scramble to secure the rights to the OS) I expect Bill had already been talking to Seattle Computer Products about selling a version of BASIC on their 86-DOS because he was all about the hustle and he wanted it to be on every computer. He likely saw the opportunity and would have asked about licensing it as a product Microsoft could sell.
3) The PC team finds out that Gates can supply both the OS and BASIC and presents to John: "Option A: We can get BASIC from Microsoft and CP/M from Digital Research" (most popular OS and most popular language), "or option B: we can get both BASIC and an OS that is similar to CP/M from Microsoft."
I am suggesting, that given that scenario, John could have expressed a "preference" (always leave it in the hands of the team you delegated the decsion to, to decide, but you can express a preference) that they go with option B. Putting myself in his seat, I might have spun that preference as "Microsoft's OS isn't out there, but neither is CP/M for the 8086, and this way we would only have to deal with one vendor for software integration." All straight up, all above board, reasonable argument.
What I'm saying, is that in making that choice, it gave John something he could use with Mary, "Hey we're going with your son's company for the language and the OS" and she would be happy about that. I'm also saying that I would not be surprised that had a product person said "We going to be fighting headwinds with a microcomputer that doesn't run CP/M as that is the one that these small businesses are using, we really should go with CP/M-86 here." And having the chairman push back with "Why don't we do this, IBM has a good reputation for its operating systems on 'real' computers, we'll take the Microsoft product and rebrand it as 'PC DOS' and it will be an IBM thing which businesses already trust, how about that?"
Also a reasonable thing to do or choice to make. And it worked out for them and Mary appreciated John's support in helping her son's business. Which was helpful to John as a board member of United way. So two for one, IBM gets an OS and John gets a favor credit with Mary.
But I also point out that this is rampant speculation and no more accurate than a large language model that uses statistical likelihoods to write sentences. :-) The only other bit of information I can add is that I was working for IBM the summer of 1977 as an intern, and my boss knew I was trying to save up enough money to buy a CP/M computer so he gave me a secret peak at how IBM was going to take over the microcomputer market so maybe I should wait. He showed me an unreleased product, the IBM 5100 running BASIC, it had a built in screen. It was a computer by engineers, for engineers, and no one would buy anything else :-).
Even young me knew that was not gonna fly :-). But the IBM of that time was both predatory (they were being sued left and right it seemed) and cheap, and they thought they were the smartest people in the world. When I went to the PC presentation they gave us in 1981 at USC I thought, "Hmm, not a 5100, but a bunch of their own software with third party chips." That was very on brand for them.