Intel wanted to release an 8 core mainstream CNL-S in 2016 but this project died because 10nm was coughing up blood and had no reasonable chance of going into production in time.
So to give OEMs something new, they added Kaby Lake to the roadmap as a relatively low-risk way to get something better out, and they also added Coffee Lake, which they could increase core count with because they knew they'd have another year's worth of process advancement + more time to fine-tune the circuit design as well as the platform itself to support the higher core count.
It appears that they also threw in an 8-core CFL. I don't think this will be on a 14nm+++ or something like that, but they will have still more time to wring out more performance from the physical implementation to support the still higher core count. Also, additional process maturity should help them be more aggressive in binning for frequency.
So, while AMD Ryzen certainly impacted Intel's CFL release schedule (forcing Z370 on the OEMs, for example, rather than having them wait for the proper Z390), the truth is that Intel's roadmaps are first and foremost dictated by what its OEM customers (organizations that buy multi-billions of dollars' worth of silicon each year) want more than anything else.