Silicon is bodybuilding-hard. It is extremely hard so there are few competitors, but it is inherently a series of extremely expensive coordination problems. To churn new architectures every couple years takes an oiled machine of thousands.

Don't forget that Intel had a few decades where nearly all software was written for their x86 chips. This reinforced every computer needing to have intel, and only recently has the move to web apps made it easier for devices to use something other than intel.