I could be wrong here but it's my understanding that the PC clone market was an unintended consequence of 1) doing the job in a hasty slapdash way with off-the-shelf components 2) handing control of the OS to a third party, namely Microsoft, without an exclusive license. IBM had just one tiny bit of proprietary knowledge, the BIOS, and once that was out of control, the PC clone market was up and running.
There was a time when Microsoft was the promethean hero bringing computing power to the masses. They really earned their dominant position back then, compared to how closed IBM and Apple were. Granted, the architecture and software were crap compared to many of their competitors, but Gates correctly analyzed that having the most open platform would eventually solve those problems.