The problem here is that ARM & x86 have very different memory models, not that the ISA itself is a big issue. Re-compiling for ARM is super easy, yes absolutely. Making sure you don't have any latent thread-safety bugs that happened to be OK because it was on x86 that are now bugs on ARM? That's a lot harder, and it only takes a couple of those to potentially wipe out any savings that were potentially had, as they are in the class of bugs that's particularly hard to track down.
If you do have hidden thread safety bugs you are only one compile away from failure, even on x86.
Some function gets vectorized and a variable shifts in or out of a register? Or one of your libraries gets rebuilt with LTO / LTCG and its functions are inlined.
If your code was wrong, any of that can ruin it and you're left trying to figure it out, and requiring your developers to use exactly one point release of Visual Studio and never, ever upgrade the SDK install.
I agree to some extent but don’t underestimate how much this has changed in the cloud era: it’s never been cheaper to run multiple ISAs and a whole lot of stuff is running in environments where switching is easy (API-managed deployments, microservices, etc.) and the toolchains support ARM already thanks to phones/tablets and previous servers - so much code will just run on the JVM, high level languages like JavaScript Python, or low-level ones like Go and Rust with great cross-compiler support, etc. and hardware acceleration also takes away the need to pour engineer-hours into things like OpenSSL which might have blocked tons of applications.
At many businesses that is probably over the threshold where someone can say it’s worth switching the easy n% over since they’ll save money now and if the price/performance crown shifts back so can their workloads. AWS has apparently already done this for managed services like load-balancers and I’m sure they aren’t alone in watching the prices very closely. That’s what Intel is most afraid of: the fat margins aren’t coming back even if they ship a great next generation chip.