Intel has had a process lead, but that's not the only reason they make abnormal margins.
- Lock in. AMD's the only viable x86 vendor and they've been off in the weeds after their glory days that culminated in x86-64 and NUMA x86 architecture
-Ecosystem. Intel invests heavily in things like compilers and standard libraries and so forth. They pay to have good software developers enrich an ecosystem that favors their processors
-Microarchitecture. They frankly have very good hardware engineers.
ARM came to prevail because Intel took their eye off the ball in the low power space. Recent Atom family designs have made a strong showing in that space (in part due to software developers creating remarkable ARM emulation, in part due to excellent hardware design, and in part due to the business call to compete at more typical (for the market) margin). The 'ARMs sip power' reality was (unreasonably) extrapolated to "they'd kick ass in the datacenter", but now studies are being done and the ARM server designs are losing both on raw performance and performance per watt to the Intel offering (e.g. one done by CERN did open power 8 v. aarch64 v. two x86 variants (atom and xeon e3) and the x86 variants won most everything (except POWER did SMT better than most, but even that fell apart most of the time).