Why? If anything, this whole fiasco shows how misguided it was changing our entire national economy around a singular resource. In 20 years, our biggest export went from automobiles and auto parts to petroleum. Every other industry either went in decline, was neglected or didn't adapt. Things like machinery and equipment (agriculture), forest products like timber, newsprint and wood pulp.
Alberta tarsands oil may be plentiful, but it is one of the dirtiest oils on the planet. We do extreme environmental damage extracting it. To export it we need to run pipelines through some of the world's most pristine natural forests and freshwater areas. A smarter and better investment would have been trying to become a world leader in renewable energy, solar, wind etc. But it's a perfect storm of things messing it up for Canada. Rising wages in China have made automobile companies decide that Mexico is a better option than Canada and it's why Ontario has lost more and more contracts to build vehicles and parts.