Boxing has significant cultural visibility in the UK... We make a lot of our sporting winners & are quite a sports-obsessed nation, so we zero in on the successes.
We invested a lot of dosh in amateur boxing in the run up to the 2008-2012 Olympics (New Labour in Britain invested a lot in "community" sports from 1997 onwards, which took a decade to tell, i.e. a lot of boxing gyms got makeovers & became places you could go to train & keep fit rather than "If you're here, you bleed" -type places; thus, ten years later, they were showing results. This, I'm certain, drove up attendance & participation for the sport on all levels: if you get the kids through the door without having this "YOU MUST FIGHT TO THE DEATH" thing hanging over them, those who discover a spark of interest/show natural talent that they didn't know they had will naturally follow up on it because they're encouraged to continue with something they're good at rather than being forced into something. The old-school gyms were dying in Britain when I was a kid—not one of them in the various places where I grew up would take you on if you weren't willing to fight there & then, because they were all run by bitter old men & had no funding or proper programmes in place; hence they were all run into the ground & participation in amateur/junior/pro was declining). It's paid off, as I've said above, & boxing classes are now something anyone can do (who keeps fit/works out).
This is how you build a sport up from the grass-roots in the modern age. I'm not very patriotic, but this is the sort of success story people should be shouting about from the rooftops, IMO: without that investment & encouragement & opening up ofthe sport (to people who don't wanna get hit, women, youngsters, people who just wanna get fit), we wouldn't have had the Olympic success & following on from that our flourishing pro scene (which again leads on to big crowds as media becomes interested in broadcasting it).
But you need that investment, & you need a willingness to change that as I said just wasn't there when I was a kid.
Twenty-something years ago, first time I walked into a boxing gym in South London, with five of my teenaged mates who fancied a go, we were thrown in, one by one, with the hardest nuts there, guys who were much older than us & who'd had actual fights.
All of us got the shit kicked out of us; only I (who came from a boxing family—my old man, my uncles fought pro, loads of cousins fought amateur, whole family been around the game for years) went back. Covered in blood afterwards, heads ringing, the old boy who ran the place told us; "If you don't wanna fight, then fuck off 'cos I can't be bothered with you."
Guess what? Most fucked off & never came back.
This was the prevailing (1930s-esque) attitude that reigned for years in Britain & it nearly killed the sport. Only a massive conceptual change on the level of grassroots participation saved it & turned it into the massive success story it is today.
TL;DR: The government put money into it on a community sports level; far-sighted modern people got involved in the training & admin side. This drove up participation at all levels & the amateur/pro game flourished because of it, just 'cos of the influx of new blood.