It's crazy that the only serious density built along this corridor was in the 1960s/early 70s
I would suggest to you, that general trends in growth aside (The City did have a real slow down in growth in the 80s); that some of the planning mistakes on Broadview, like those in St. Jamestown caused a counter-reaction.
In the case of Broadview, the row of highrises up towards Mortimer largely cut off the view for everyone else, no access to the valley was added, not one public lookout, the buildings also had a relatively poor relationship to the street and no retail or other animation at-grade.
The community balked and went hard NIMBY.
I think it conveys an important lesson, development done well tends not to produce the same strength of counter reaction as development done badly. (not always true, some areas are utterly change resistant, but I digress). Still, on balance, make a hash of things and don't be surprised at seeing opposition derail what you were you up to.
This is true in non-development as well. Extreme and/or poorly sold public policy can produce a ferocious reaction, be that policy reactionary or progressive.