The 10nm delay is of course legendary at this point, but 14nm was itself also about a year behind schedule. In early 2013 Intel stated Broadwell 14nm would be out that year. It didn't come out until Q4 2014. And Intel's Fab 42, which was originally scheduled to open in 2013 as their first 14nm fab, only just opened this year. Intel ended up needing to re-fit existing fabs to be 14nm instead.
So before they faceplanted with 10nm Intel first stumbled with 14nm. 2 generations in a row of issues.
Proper leadership would have taken this risk seriously, and would not have tied up microarchitecture development so much to process improvement. Basing your strategy so fully on Moore's Law keeping up is a recipe for disaster. Clearly Sunny Cove works on 14nm (that's what they're releasing next year!), and they had all the technology available to release that in 2018 too - maybe with lower clocks and core counts.
Seems like a classic textbook case of a large coorporation not understanding how to change their ways, ending up being beaten by a more agile smaller competitor. Oh well, hindsight is 20/20.
So before they faceplanted with 10nm Intel first stumbled with 14nm. 2 generations in a row of issues.