Nearly two thirds of Canada's population live within the Windsor-Quebec City corridor - some 40 million people. Similarly Vancouver, BC - Portland, OR has relatively high population density. Population is not the reason for rail failing here.
Ok sure but when I say Canada I am talking about the entire country. I support a cheap, fast line connecting Toronto with its populated neighboring cities. And sure, something between Vancouver and Portland would be fine. But it is not feasible to, for example, connect Vancouver and Toronto with rail. In Europe, you can take rail from London to Athens. I want that in Canada but you have to go through vast amounts of nothingness to do so. Population IS the reason for rail failing here.