From the article:

A WIRED investigation shows Kofsky is also the person posting as PsychoticMammal. The account has posted personal details that precisely match Kofsky’s résumé, and has linked to a little-followed Instagram account dedicated to photos of Kofsky wearing preppy outfits. A review of publicly available material from data breaches provided by Constella Intelligence shows that Kofsky’s personal email address was used to set up a “PsychoMammal” account on a photography site. Furthermore, the PsychoticMammal name was used on Poshmark by a user whose avatar is a photo of Kofsky. It was also used on Tumblr by someone who linked to—and claimed as his own—a Blogspot maintained by a user named Aaron Kofsky, who posted personal details that match details of Kofsky’s biography.

Apparently, this guy left a huge trail… Edit: plus data breaches…