"Cause of the collapse"
Read on. The section titled "cause of the collapse" describes an increasing amplitude of vibration, fed by the anelastic flutter. That's resonance...
The section which refutes resonance is, in fact, refuting a particular resonant mechanism and then covers itself by saying that the whole issue requires complex multi-dimensional modelling to be sure what the *exact* cause was, but to all except the aerodynamic purists, it is a simple resonant reaction between the wind-derived forces and the bridge vibration mode.