Hmmmm.... do you really think that this was the reason why developers flocked to iOS and Android? The expectation/hope they would not be fucked over like those who had burned fingers with Microsoft?
Or could it be that it was really clear that developing and marketing apps for iOS and Android had (has) huge market potential and straightforward way to sell apps and see the money come in.
I could be wrong, but I suspect that the reputation or history of MS dealings with partners and with their own technology was not as important as major competitors coming up and saying "Here's what you do to reach our millions of prospective buyers. We deal with distribution and growing the market, you get 70% of the sale".
Between piracy, traditional distribution channels, customers used to not spending at all, there were/are plenty of reasons why developing for PC was never that straightforward. The realistic prospect of finding 10,000,000 people willing to pay you $0.70 each was a major reason, more than anything MS did or used to do.