Michael Jordan
Into the late 80s early 90s hockey was so far ahead of any other sport for youngsters in Canada it didn't really matter who was number two. Hockey was that much more popular. While NFL and soccer have made strides, the bulk of the growth has been in basketball.
And it all traces itself to Michael Jordan dominating the sport while being a mega sports icon. It coincided with Toronto and Vancouver getting NBA teams, the NBA actually being shown on Canadian TV, and the explosion of basketball facility availability.
Hockey is 1A to basketball's 1B in Canada now. That was unthinkable 30 years ago.
People point to demographics and that plays a part of it. But it doesn't explain why all my (white suburban) cousin's kids are obsessed with basketball and don't care about hockey.