I read the article, but I can't see how the title is supported. What is for example, the second largest tech hub and how narrow is silicon valley's lead over it. I would guess that the bay area if way way ahead of anywhere else (I don't like it, but it seems to be self apparent) and the lead is not narrow at all.
I'd bet either NYC or Seattle is number two. I think Seattle comes closest in salaries thanks to the number of FAANG and similar companies with either HQ's or large branches (same time zone as California helps). NYC is probably number two as far as startup scenes.
Seattle's a tiny fraction of either and not growing in that area.
https://www.citylab.com/life/2018/03/the-extreme-geographic-...
Obviously, that's only one measure of a tech scene, but I don't think Seattle's that large.