There are a lot of interesting reasons but for the purpose of this article the one I would like to highlight is the baggage of X86 backwards compatibility. For the first time power efficiency became more important to the success of a CPU than speed. All of the transistors and all of the millions of lines of x86 code that Intel and Microsoft had invested in the PC became an obstacle to power efficiency. The most important aspect of Microsoft and Intel’s market hegemony became a liability over night.