What changed? My rough list is:
1. News bloggers got online and turned flamebait into their business model.
2. Normies got iPhones and started posting online. They never read an netiquette guide. If they had heard of the concept at all they dismissed it as computer nerd nonsense. They don't think about online communication systematically and expect every interaction online to be like talking to customer service: they get to say whatever they want, and only hear a very constrained window of things back. This backfires in all the obvious ways.
3. "Platforms" with KPIs based on engagement are incentivized to enable the largest flamewars possible and put it in as many people's faces right up to the point they start causing bad PR.
4. People with basically zero forethought thought they could fix society by being paternalistic to strangers.