This is ridiculous. ARM was already pretty much well-settled-in in the PDA way before the smartphone, so it definitely didn't "single-handedly made it happen". And during the early PDA era, when they got settled in that market, it most certainly did not win due to "low power draw". Back in the day where SH(-3) PDAs where still a thing, the battery life was measured in days out of 2 AAA cells (even for ARM devices). That was destroyed due to forced backlight usage in most screen techs rather than any change in ISA.
Today MIPS is still used in network devices, SH is still used in things like optical drives, SPARC is still used on some servers, x86 is still used on many servers and desktops and mobile devices, and so on and so forth. Do you think that there is something technical that warrants the choice of these architectures for their usecases ? Do you think that there is something in SH that makes it a better ISA particularly for CD-ROM drives ? Or that there is something in SH that made it a better ISA for some videogame console generations, then something changed and the better ISA was PPC, then ARM, then x86 again ?
It's mostly arbitrary marketing decisions, which manufacturer happened to be doing well that day, and some "historical reasons"/network effects which define these choices. There's very little difference at this ISA/architectural level, and a lot in the actual design and manufacturing level, where ARM is not doing poorly but hardly shines. Apple, Intel, AMD, Qualcomm, even nVidia all do better than ARM there.
If we the wind had blown even slightly differently some day 20 years ago, we may very well be using anything else, even say Itanium in our smartphones. And before you complain that Itanium/EPIC are hardly suited for low power, remember that Transmeta made their money selling _low-power_ VLIW processors emulating x86 instructions. And actually they were lower power than their x86 competition those days. Perhaps Torvalds would still be there rather than making Linux...