There were over 80,000 fans watching Dempsey-Carpentier in 1921-07-02. And it was 20s! Wilder-Stiverne audience just 8,000 in that heavyweight title fight. And its 90 years later, more people in the world. atschatsch
there were 120k watching tunney, you have to realize that there was no NBA, and I believe the NFL was just started, but sports like these were nowhere as close to as popular.
Boxing was the most popular sport in the country in the early 1900's, and you're forgetting the wonderful creation of television hadn't occurred yet. Wilder Stiverne had 1,240,000 viewers that's impressive no matter how you spin it.
Dempsey vs Carpentier was for the Heavyweight title, while Wilder vs Stiverne was merely for the WBC belt... huge difference. Plus, baxxin' isn't nearly as popular in the States right now of course. In Europe crowds like that aren't such a big exception when Wladschko or Vitschko fight some poor bloke
As others have said boxing isn't as popular as it was back then, it isn't even as popular as it was 30 years ago. Boxing has suffered because of it's inability to unify itself in to a coherent organised sporting body like the NFL and NBA. It's just a group of self interested sanctioning bodies and promoters who only work together when it suits them. So while all other sports like Golf, Tennis, F1, Basketball, football etc have flourished, boxing has become a fringe sport. You only have to look at how the US amateur game as literally died in the US. We are beginning to see the results of this in the pro game but give it another 20 years and I think a US Champion will be a very rare thing if something is not done to revive the US amateur game.