I've tried to write a longer piece several times on this and keep hating what I come up with so here's the shortened version:
Cohost, being a feed based site, doesn't have a "shared space" that everyone on the site can reliably see and participate in. What that means is that there is no one "site culture" because tons of different site cultures are being formed in cliques across the site constantly, and by extension it was never going to be possible to improve the site culture to deal with harassment—moderation was always the only viable option.