Intel has a history of changing the x86 constantly in small ways, which forces the cloners to follow suit. By the time the clone-chips makers catch up, Intel is ready to change again. Intel used their advantage in any area, to help push support for the other two areas. Momentum builds momentum. But changes in each of those markets, may have just eroded the reasons to follow Intel.
Lets look at each one individually.
Intel keeps changing the way the processors are connected to the motherboard. Monopoly maneuvering defined. These chipsets are as important to a computers performance as the processor itself. Second sources, and lower cost alternatives would come later. This is why there are 10 different connectors in the PC world.