The real reason for Intel's 14nm shortage is obvious. Apple.
They probably made the deal with Apple to be their exclusive modem supplier a few years earlier, when they assumed they'd have 10nm in volume and 14nm fab space didn't matter. They were wrong, and producing a huge run of modem chips for iPhones was responsible for the shortages last year, which then eased a bit after they had enough to supply Apple through Q4 which is their busiest quarter.
Right now they are building a bunch for the next gen iPhone, but will once again be able to ease off thus Intel's prediction that the shortage will ease in Q3.
Biting the hand that feeds IT
