At least according to this article in 2017 [1], it looks like that was because of SoHo's soaring rents (because there's tons of great shopping which brings a lot of people there). It was also common across the country at the time.

It's apparently back and better than ever though [2].

And anecdotally, everyone I know shops much more in SoHo than they did a decade ago, even if the center has shifted to Williamsburg/Greenpoint and more thrifting / vintage stores.

[1] https://www.nytimes.com/2017/08/23/nyregion/soho-empty-store... [2] https://equicapmag.com/real-estate/soho-retail-rebounds/#:~:....