Lots of ways. Typically people meet through conferences, where high-impact work is published. It's also not uncommon for researchers to cold-email each other ba

Lots of ways. Typically people meet through conferences, where high-impact work is published. It's also not uncommon for researchers to cold-email each other based on mutual interest or friend-of-friend connection. Things like Google Scholar can be used to get emails about when your papers get cited, so this can spur some discussion / collaboration as well. Honestly, you could email an author on this paper and they would probably tell you directly.