DJL.
As nobody else has answered you I'll try & give you the basic idea.
A dominant tackle will be called when the defense propels the attacking player towards his own goal line.
the rule was brought in to give some reward in the ruck to the defensive team for basically playing within the spirit of the game & to counter negative style game plans like Andersons, Stuarts, Ryans etc, that was not within the spirit of the game. Their plans revolved around quick rucks & play the balls with the attack running to the line & dropping to their knees & succumbing in the tackle. The old rules meant that the defense had to roll away imediately giving momentum to the attacking team & an unfair advantage.
The rule was sort of silent rule for a few years, more of a an agreement between the refs. But it meant an end to Andersons game plan for ever.
His decision was to persist and bang our players heads, but it was clearly finished with.
More than anything else, I believe this was the major contributor to his sacking.
