Dept. of 20-20 hindsight

I asked this already, in the comments to another post, but it’s been nagging at me:

Why did the Conservatives spend two years buying pre-writ ads against Stéphane Dion, in French, in Quebec? There wasn’t a single month in that entire time when the main opponent in French-speaking Quebec wasn’t the Bloc Québécois. And the Conservatives just let them be. Doesn’t seem clever in retrospect.