CISC couldn't go that fast without using 125 watts.
RISC could use 99% less power and go half as fast.
Everybody bought "Intel inside", even though it drew a hundred times more power.
Yes, mobile is one reason people now care more about power consumption. Waking up to it's effect on datacenter costs is another.
"The goal was always to make devices as efficient as possible"
If that were, CISC would have been dead on arrival.
Intel has pretty much admitted that CISC will be dead soon unless they cut power usage by 99% because suddenly power usage is more important than brute speed.