I happen to be an expert on the subject.
1990s: Video games killed comics. Killed dead, nearly 1000% sales loss
2000s: average indie sells 30k, average big two sells 300k and bleeds numbers every month
2010s: Big two collapse, numbers for all US
comics normalize at 30-20k.
This has been a 20 years long death coming.
Why did it collapse?
1. Gringos hate comics. They think it's "kiddie shit" with no culture. All the crap of the last 20 years did nothing but cement that notion. Only gringoshit that sells is, in fact, kid comics.
2. US Comic industry completely failed to adopt digital colouring into their format, making their comics largely unappealing for art hobbyists.
3. Publishers strongly favour sweatshop mentality and almost exclusively hire the cheapest artists, writers and eschews editors
4. Rich kids obsessed with the medium basically bribe their way into jobs and give their friends jobs in turn. They have no idea how to write a book but it doesn't matter, they are rich.
5. Self-publishing venues have no quality control whatsoever and a large number of their books end up abandoned.
6. No attempts at creating organized space to independent comics has been done
The one thing I don't understand is why gringos abandoned webcomics when both Japan and even Korea learned to make them profitable
I also don't understand why there's an indie comics drought with almost no 2016-2020 arising people's interest