An x86 monopoly in the late 80s was a thing, but not now.
Today, there are sufficient competitive chip architectures with cross-compatible operating systems and virtualization that x86 does not represent control of the computing market in a manner that should prevent such a merger: ARM licensees, including the special case of Apple Silicon, Snapdragon, NVIDIA SOCs, RISC-V...
Windows, MacOS and Linux all run competitively on multiple non-x86 architectures.