I have not read anything but here's my understanding... Hot off their success in the 80s with the desktop market, in the 90s Intel decided to go up market and

I have not read anything but here's my understanding... Hot off their success in the 80s with the desktop market, in the 90s Intel decided to go up market and target workstations, datacenter, and mainframes. They launched the P6 architecture with HPC in mind and eschewed power efficiency. By the mid/late 90s they didn't have an x86 product that could work well in the mobile space let alone the embedded space. The recognized that the laptop market was poised to explode and started work on Pentium M which eschewed their P6 derived Netburst architecture for something closer to the P5. ARM wisely chose not to compete with Intel and instead went for markets Intel wasn't in. This included mobile and embedded. At the time Intel was trying to optimize x86 for Laptops (Pentium M / Core), ARM was working down market from embedded to microcontrollers (ARM M). When Smartphones started to take off, ARM was positioned to be the processor of choice due to it's focus on low power and efficiency AND the fact that anyone could design their own SoC around it. Intel on the other hand was still trying to scale down x86 from the laptop space and chose to develop their SoCs entirely themselves. Intel also has this on going problem of eschewing SoCs for discrete chips because they want to sell you as many chips as possible. Fast forward to today and Intel's Atom line is comparable to ARM's high performance line (ignore Apple) in terms of performance and battery but it lacks the SoC integration you see in products from Qualcomm, Mediatek, and Samsung.