Fundamentally, ARM Holdings is what Antitrust legislation was supposed to break down. They own the "ARM" name and control who can license the ARM IP and most importantly, how.

Ampere, the folks behind a lot of ARM servers, are by contract barred from getting into the market of making ARM chips for phones, desktops, or otherwise. That's the form of their license: Server-grade 96-core behemoths running at 3+Ghz and with the thermal output of a small space heater.

ARM holdings sets all sorts of weird restrictions and forces market segmentation to make sure that nobody "Accidentally" makes something that they don't immediately approve of. Qualcomm is basically locked into making phone SoCs for all eternity until they renegotiate their license with ARM holdings. They're in a shit situation because they have competition all over the place (Allwinner, Rockchip, a legacy Intel series, NXP, and Samsung to name a few), letting ARMHoldings bully them into not making something that rocks the boat too hard.

Apple pulled a massive show of force in making ARM license them desktop grade chips. You see, Apple has been a license holder for ARM for a bit now (with the Ax series chips) and makes up, ballpark, 15% of worldwide phones and now >50% of US phones. Apple had already idly said "we could... you know, not use an integrated solution" when they fiddled with Intel's radio baseband.

For ARM to try and sue Apple for breach of contract for developing the Mx series of desktop class ARM processors and get away with it, they'd be putting their market share dominance in four different major markets at risk. Qualcomm can't do that.

So that leaves Microsoft, who does not want to get into the processor fabrication business and who is still reeling over the antitrust lawsuit 20 years ago (which, I'll point out, was mostly over a shared text mangling library, for what it's worth) out in the dust looking for options, and the option they get is "Whatever Qualcomm will ship them."