Another reason could be that his biggest success was an issue that earlier Liberals had advocated - free trade. This could have made Canadians even more suspicious of him. But the record of his successor, the Liberal Chretien, is little more than the implementation of the agenda Mulroney himself set with regards to none other than free trade, and in balancing the budget. Obviously, the Liberals have not waded into the other part of his agenda, constitutional reform, which was held as the cause of the Conservatives' destruction. This is the result of the demagogy that has served the Liberals well in the past.
Any real leadership is destroyed and replaced by smarm or a more honest loser attitude.
This obscures the plain fact that they've been in charge more than seventy-five years out of the last hundred. You can see what the hoax that keeps them in power is. Since Canada was born in the age of the Robber Barons, who were used to help build the country, this is plausible, especially since the Canadian version was just as corrupt as the American one. But this had led to an anti-enterprise ethic that has been perpetuated by the old upper class in this country going into trade. Now that the Clinton term is over, though, Americans might find this habit useful.