The main issue was that it was submitted late Friday night SF time, meaning it was overnight or Saturday everywhere in the world when the post had its chance on the front page. The flagging was minimal relative to the vote count and had no effect, and the flamewar detector would have been turned off sooner if moderators saw it sooner (it wasn't really a flamewar, just a lot of comments). It still spent 10 hours on the front page.

None of this is anything out of the ordinary; this kind of thing has always happened. The only real story here is that moderators sleep sometimes.