The issue is that mfg of cpus at scale is very costly, and short of a large scale, the per-unit cost to cover tooling is higher... lower margins, less profit, higher cost to the customers. Per-Unit cost, and relative throughput is why Intel rules the roost for the most part, even in server.
I've looked at some of the costs of ARM servers, and they're way more expensive than they should be (compared to the cost going into phones)... I would think that may eventually become competitive... though Intel has a bit of room to lower pricing and still make money to compete.
But the chip you get in a smart phone is not what you get in a server. For one, I/O is very different and it includes things like 40Gb network silicon.
I've looked at some of the costs of ARM servers, and they're way more expensive than they should be (compared to the cost going into phones)... I would think that may eventually become competitive... though Intel has a bit of room to lower pricing and still make money to compete.