You forgot problem 4: You need to provide your VC ownership a profitable exit.

This plays off problem 3. Growth-focused social media platforms don't want to remove anything but the noisiest noise, because there's still a pair of monetizable eyeballs behind most sources of noise. In fact, if you can be particularly noisy, you generate drama, which makes the platform emotionally salient and thus stickier.

How this applies to 4chan is vague since 4chan isn't exactly a growth platform. Moot's VC ownership was his mom's credit card[0] and his exit was "panic selling to hiroyuki because Hollywood actors' lawyers are breathing down my neck". Hiroyuki himself is incredibly sketchy. As far as I can tell, he bought 4chan mainly because 2channel got rugpulled by his domain registrar[1], after 2channel also had a massive data breach. Funny how history repeats.

Anyway, imageboard ownership being a fractal mirror of the incestuous bullshit going on in big tech and far-right politics aside, once a social network or forum becomes big enough to be 'known', it tends to stick, because moving off those platforms is a collective action problem. So between you holding your friends mutually hostage and the drama from letting the dumbest idiots post on your site, you've created a powerfully addictive socialization substitute that can be manipulated to make people do whatever. Quality posters and value don't matter; in fact, once you're established you want the quality level to go down.

Digg collapsed because they replaced the entire website with something completely different. They didn't fail to moderate the community, they just shut it down. It'd be like if tomorrow Facebook said "we're not doing user posts anymore, we're just going to have a bunch of comment sections for videos from legacy media outfits". Everyone would leave immediately because there's no more mutual-hostage-taking by your friends.

[0] This is not to be confused with Canvas, a similar imageboard platform also started by Moot that lasted like a year.

[1] If you believe the guy who stole the domain, the data breach rendered 2channel unable to pay domain hosting fees. That being said, the guy who stole the domain is also the owner of 8chan and a huge QAnon nutter, if not Q himself, and stealing your client's website because they ran out of money is an extremely malicious move.

As far as anyone knows, hiroyuki got the money to buy 4chan from Good Smile Company. Yes, the people who made Nendoroids.