It’s in ones best interest to look like they have a close competitor, but in reality so distant it won’t catch up.
It happens to many business branches and the last barrier is the law prohibiting cartels and monopolies but it does not work globally.
Around cocoa some days ago a cartel formed and there is other examples where we only have one real provider left.
One big pro for the way our capitalist markets work always was that the competition will drive innovation. In the end of course this cannot work anymore and we can see many businesses where consumers just have to take the products that one big player offers.
Look at Intel processors which are built into nearly every device nowadays. Of course in the recent history AMD started to face them again but it will be a long time until they even come near the market share to really compete.
Yes there is other CPUs as well but who even speaks about them or considers (knowingly) buying a device with something different than an Intel CPU?