Why did Howard Dean's scream destroy his campaign?

[Beet]

For me it was always my view that the Scream distracts people looking back from the real cause of his loss. The fact that he just lost Iowa badly.

Right. When you lose, the press becomes like pirhanas or sharks, looking to reinforce the narrative, and that's what happened with the scream. Dean lost Iowa because Kerry and Edwards "leaned in" and started co-opting his anti-war stance.