And the Superbowl gets over 100M viewers -- a two-orders-of-magnitude difference.

[edit]

Yes, there are literally more than 80,250 (MetLife stadium's capacity) fans of boxing in the US. However e.g. the Kingdom Arena (location of Fury v. Ngannaou) seats about 30,000. If there were a 17 week boxing match season in the US, it clearly would be a much smaller draw than gridiron football, and that doesn't even include the college game, which has 8 stadiums that seat over 100k (and 6 more that are larger than MetLife).