The two employees said they couldn’t recall the exact reason for their fleeting celebratory behavior but that they believed it may have involved sports, which they frequently talked about, the source said.
Once you’ve accounted for the jerkiness of the video, it doesn’t seem outlandish, given the sorts of things men do in New York, particularly when talking about sports.
A commenter at The New Yorker adds that Edward Jay Epstein, who brought up the dance of joy in a New York Review of Books article, is a conspiracy theorist:
Many years ago, Mr. Epstein had written about the diamond industry. I knew a top adviser for De Beers,who couldn't believe how Mr. Epstein had invented so many details to support his claims. The adviser decided then that he would never again read anything written by this conspiracy theorist. He called Epstein a "sensationalist". I myself wonder why the NYRB would publish an article that had nothing to do with books.
P.S., a commenter points out that Epstein's website has more videos that allow you to better evaluate the competing theories.