Saw that too, interesting map. Perhaps this is more a comment on the Mets, but even around Flushing Queens, the Yanks rated higher than the Mets.
That’s a pretty common phenomenon in sports, where some teams have a national fan base due to the storied history of the franchise and/or the national exposure over many years. The Yankees, Red Sox, Cubs and Dodgers are good examples of this in MLB. The Dallas Cowboys, Green Bay Packers and (maybe surprisingly) the Pittsburgh Steelers are good examples of this in the NFL. Even the NHL has their versions of these larger-than-life franchises: mainly the “Original Six,” but the Philadelphia Flyers might belong in that group, too.