I think the Newton was the first major use of the architecture outside the Acorn Archimedes.

"...an advanced, low-power processor was needed for sophisticated graphics manipulation. He found Hermann Hauser, who had developed the Acorn RISC Machine that utilized what became known as the ARM architecture, and put together Advanced RISC Machines, now Arm Ltd."

https://en.wikipedia.org/wiki/Apple_Newton

Around this time, DEC also chose to implement their StrongARM, so that pushed into embedded.

https://en.wikipedia.org/wiki/StrongARM

It cost them an ARM and a leg.

Nah, Acorn was first.