The PReP/CHRP was a venture by Apple, IBM, and Motorola (but primarily IBM) to allow companies to build OSes for a common platform. Apple didn't want to participate in the end. But like other ports of NT to MIPS and Alpha (Alpha enjoyed much more support until Compaq dropped support), the popularity was well beneath the dirt cheap in comparison x86 platform.
https://en.wikipedia.org/wiki/PowerPC_Reference_Platform
https://en.wikipedia.org/wiki/Common_Hardware_Reference_Plat...
This had nothing to do with Microsoft's monopoly. And nothing to do with exclusively 'desktop' PPC -- remember, NT4 Server also had PPC support through SP2. IBM's intention was for servers, not desktops (though they did produce compatible laptops/desktops), to support operating systems such as AIX and S[l]o[w|l]aris
AIX isn't exactly a desktop OS.