I want to push back on this part:

Only if Microsoft acquires a major CPU chipmaker.

In the USA, and other parts of the world, a small number of Billionaires are buying up everything. A small number of wealthy people could each own a part of the supply chain and for it on the vast majority.

For extra enforcement, add in a legal or cultural push for reporting or shunning violators through the media companies owned by that same group.

They make their own ARM silicon for datacenters, hypothetically they could just scale that down for consumer devices and there's your vertical integration.

Conversely if Apple ever wants to enter the datacenter market, they could scale their M-series silicon up to meet that industry's demands as well.

Doesn't matter, Microsoft already sell computers, i.e. Surface. One can still buy computers from other manufacturers. They can buy an instance of the entire stack (pretty much as Apple did) and there would still be alternatives.