What killed hockey was the introduction of goons whose only talent is to start fights to break the other team's momentum.
This tactic was introduced by Punch Imlach when he coached the Buffalo Sabres after expansion.
The Sabres were terrible, so he used Tracy Pratt as a goon.
There were always fights in hockey, but it was only after expansion that fighting be came part of the game strategy.
Another thing that hurt hockey as a spectator sport was the switch from advancing the puck along the boards to taking it up the middle.
Concur totally. A Gordie Howe-Doug Harvey fight was one thing. A Tiger Williams-Dave Schultz fight was something else, more like a scripted event.