It's great that Amazon has ARM based stuff, but it's something proprietary they're purchasing in large quantities from a manufacturer they have a very close relationship with. Undoubtedly the physical hypervisor platform and motherboard these things are running on is something totally bespoke and designed to Amazon's unique requirements.
I can't pull out my visa card and go buy a (atx, microatx, mini-itx) format motherboard for an ARM CPU, the CPU itself, RAM, etc, and build a system to run debian, centos, RHEL, ubuntu whatever on.
This means that, sure, you can get an EC2 ARM based server, but it's something you can't physically own and you'll be paying cloud based service rates forever if you want to keep running it. There are some categories of business and government entities where not having things on-premises, or fully owning and controlling the hypervisor all the way down to the bare metal, is a non starter.
If the ARM platform Amazon is buying becomes truly price/performance competitive with a single/dual socket xeon or threadripper/epyc, it also gives a possible competitive advantage to Amazon over any medium-sized cloud based VM provider out there currently selling (xen, kvm) based VMs on x86-64 hypervisors.
Based on what's available on the market right now I see no signs of there being a viable hardware-purchasing alternative to Intel or AMD based motherboards and CPUs.