first of all, their 10nm process is only being used on their low powered mobile chips, the main reason for that is intel can't make 10nm work at higher voltages/clock speeds. This is why 10nm has been delayed as long as it has (that and terrible yeilds)
The root of intel's 10nm problems can be found in 2011, at the time intel had kicked AMD in the teeth with SB and bulldozer was a trashy mess. Without any real competition, intel set it's gaze on ARM, and has been working to make it's x86 chips competitive with ARM in the mobile market. that's been intel's focus for the last 7 years. they never really expected a real challenge from AMD and laid their plans on sinking ARM. Intel's 10nm was originally designed to do just that.
Between the low yeilds and AMD's resurgence, intel has been struggling to make a chip designed to crush low power low clock chips compete against AMD in the HEDT and enthusiast spaces. It simply can't, so they've been stuck running in place on 14nm as they try to hold off AMD long enough to create a 7nm process that can work in the HEDT market.