Taking all of your assumptions together as givens:
- Intel's unacted claims around patents 7 years ago were valid in the first place.
- No major government acts against the action because of simultaneous individual tentative politics in each and every single one. Including the EU, which has indeed blocked deals between 2 US companies even after the FTC has approved the merger (e.g. GE+Honeywell).
- Qualcomm concludes the best way to squeeze the most money out of Intel is to shitcan x86 completely by cancelling the cross-licensing deal (despite INTC having higher revenues than Qualcomm and selling competitive CPUs in markets it doesn't even target at all).
- The result of shitcanning x86 by cancelling the cross-licensing deal is people go exclusively to ARM
It's still not clear why Qualcomm would have free reign on the x86 PC market it just ate the cost of destroying. MediaTek, Samsung, and Rockchip already make consumer ARM laptops - the first two often beating Qualcomm in performance anyways. Apple also has their own walled garden offerings in the consumer ARM device space. Qualcomm's biggest advantage in the PC space was their exclusivity agreement with Microsoft for Windows on ARM but that is already dying at the end of the year. So say all the above wasn't a concern, Qualcomm really did dump billions into Intel just to stop making their processors and it was allowed, how is Qualcomm going to get their money back at all let alone better than squeezing Intel normally without first killing its main source of revenue?