These have always been the real crimes in my mind.
Ballmer wasn't an idea guy, he was a top-tier salesman / cheerleader, and he definitely "understood" what actually made Microsoft successful (put out a product, then allow third-party developers and support to extend it / support / learn it inside out and be a VAR).
Ballmer made the same mistake a lot of people in that era made, which is that they didn't realize the software was the most important component. The era of "killer hardware" never actually existed in the smartphone space, because you had a limited form factor to begin with. You couldn't cram an NVIDIA GeForce 8800 Ultra in your phone, so your software had to be useful and on-point.
I think Satya saw the entire Windows Phone debacle as a failed experiment and probably looked at Apple / Google and just threw his hands up in frustration.
Getting developers onboard for Windows Phone was critical and not enough time, money, and attention was spent doing that. I think there was a degree of Microsoft arrogance there, along the lines of, "We're Microsoft, of course they're going to develop for our platform..." Meanwhile, in 2024, the Windows App Store is still a barren hellscape compared to even the App Store for OS X and you don't even want to talk about Google Play Store and iOS App Store vs Windows Store.
The prophecy was fulfilled - software will eat the world.