Good one.
I think the one question that gets asked now and then, is what happened in (USA) scene after the sort of 2005'ish peak has been done and by 2010 or so... way way less happening. Dilloway mentions financial crash, that caught the noise a bit later. First people could afford beer, weed and noise. Then after few years, finally realizing they can just afford weed and beer. haha.
Well, I have seen handful of times US financial crash being given as one of major reasons for downfall of some music cultures. For examples those that blossomed with CD sales.
I would strongly assume, that instead of that, what we really had was the impact of internet of the time. In 2023, it may be difficult to think how things were back in 2005, compared to just couple years later. If one didn't really experience time before. About 2005, and +- couple years, just about every company started: facebook, youtube, discogs, bandcamp, spotify and so on. Just about all things we take granted now. Guys who formerly may have had all the time in the world to get creative, go to gigs to meet someone, put out tape, put out cd and so on, and within couple of years transition time, we arrive into situation where you got marketplaces selling just about all the formerly released noise on one marketplace. You can talk to people fast online, listen to streaming audio for free of charge without knowing how to search things or communicate. You got several years of everybody putting out more stuff than they can get rid of, massive sales of thousands and thousands noise CD's thrown to people at 2 bucks each or something.
I would assume there is this combination of hot scene running out of steam + suddenly new situation where you are not just buying for the next 5 tape batch, but you got new fast rising global marketplace where you got access for all the 2nd hand stuff you missed over the years. Plus blogs, streams, etc filled with rarities you never had possibility to hear. Plus, movies, games, and countless other things. We have this joke in underground metal about one lost generation of guys. When World of warcraft came out, just about same time as social media rise, there were people who simply were immersed by gaming. So much that all former creative impulses pretty much disappeared. Still today, I talk to people and they mention they haven't got anything done, because have been so busy. And turns out, that "busy", means: games. TV-series.
In a way, entire way of how people spend their time, had such a massive impact on underground art. A lot of guys who have done it out of "having something to do", had plenty of things to do. People who were noise tourists into something new and exciting, had information overload to find plenty of other things that are new and exciting. People who formerly bought from distros and kept what they bought, had possibility to buy 2nd hand stuff and sell 2nd hand stuff easy. Back in the day, discogs wasn't the place its now (back then you could actually score lots of stuff for dirt cheap prices when tons of people listing stuff they never manage to sell locally, without knowing how valuable they could be).
And many more, but basically all reasons could be lumped in category of massive technological leap that changed so much in how things are made and experienced. It took some time until things start to stabilize.
And another thing is, that like Dilloway says, there has been lots of peaks in noise. While the USA scene may have been going downhill, you can see that for example in Finland, 2005 probably marked the moment when live noise really started to happen. That may be also thanks to technology. Finally means to quickly advertise shows to people. Noise shows in finland, from 90's to 2005 happens once in a while. Suddenly entire culture of bunker gigs, private spaces and all that arrives here. New labels start, gigs have decent audiences and so on. More bands, even more bands, and seems like from then on, things only growing to this point.
Swedish tape noise thing happened. At some point there must have been 5-10 labels besides Posh Isolation putting out gnarly DIY noisy tapes in Denmark. Russia had entire own thing going. And so on. We may talk about quiet times in USA noise, while in some other places that exact moment was the peak of activity?
Like now, there is new peak of Japanese noise happening. That's what currently active Japanese guys tell to me. Big crowds come to shows. New projects playing with interest from audience. and so on. What do we know about it here? Where would you have any information of this? Who knows..