Microsoft has a long history of abandoning partners,
Neonode had a touchscreen phone built on Windows CE in 2003
but microsoft mostly developed their phone OS with Orange UK and left them missing deadlines when they didn't deliver on time.
The companies building microsoft phones then were mostly left buring without support.
Rebooting with Windows Mobile in 2010 was after both Android and iPhone had grabbed the market,
but that didn't stop MS from driving Nokia into the ground.
But on the larger scale, phone operators before smartphones had built up gigantic specifications and standards
making it a big effort to enter into the market only to deliver old, outdated technologies.
Android and iPhone sidestepped all that by providing the simplest phonefunctionality possible and then just connect it to the internet.