Explaining success or failure is always fraught with peril and overly simplified beyond reason, but I can't help but think that Intel massively fucked up one thing and one thing only: they targeted the enterprise market. Not just the commodity data center market, but the enterprise enterprise market, the we-only-buy-IBM hyperconservative and slow to move market. The type that still run COBOL on mainframes (and still call them mainframes) because it works and recompiling isn't even close to an option. Nobody in this market wants a nominal increase in computing power if it comes at the expense of backwards incompatibility.
They couldn't have seen it beforehand because smartphones weren't a thing, but a few years after launch they had their ideal target market right in front of them. Smartphones manufacturers will do anything for an incremental improvement in power efficiency. They'll take that improvement and exploit every ounce of it both upmarket in high end phones and downmarket in android burners for 3rd world countries. And people go through phones like crazy...nobody is running software on their phones that is more than 1-2 years old, and most OSes and apps have been updated at least once in the last 3 months. A recompile and migration to a new architecture for this market isn't even 1% of the hurdle that enterprise software was.
I hope that if the Mill makes it to market, that they get the market right. I'd hate to see another innovation get the shaft because of something as dumb as some marketing decisions.