CPU side took a very long time to pare down the fragmentation. For the first ~50 years there were competing proprietary instruction sets and software stacks, languages and compilers and operating systems were vendor specific, buggy and mutually incompatible. Compilers were sold separately and expensive, apps were platform specific. x86 would have remained a monopoly if not for a licensing accident with Intel second-sourcing chips from AMD.

We're seeing a version of that replaying, with some parts better and some parts worse.

The GPU situation would be ripe for regulation to lift GPU software development from the dark ages, but companies who benefit most (NVidia) have probably become too big to regulate.