Our old friend John von Heyking offers a lucid explanation of attempts to address a political impasse precipitated by Canadian Prime Minister Stephen Harper’s perhaps ill-advised attempt to cut off public electoral subsidies to rival political parties. Rather than adopt American-style political fund-raising, the three opposition parties--with nothing in common except an inability to raise money according to Canada’s rules--have entered into a political marriage of convenience to bring Harper down. Von Heyking explains why they’re unlikely to succeed and how John Locke helps us understand why. 
You are wrong, there are a few things in common with the three opposition parties.
To name a few, they are far more left than the current minority government in power and together they hold more power than the conservatives.
Unlike the U.S.A., Canada does not elect parties, we elect Members of Parliament and traditionally the party with the most seats gets to make the cabinet. If they have a majority they can pass laws and regulation all they want but without the majority of seats they need to work with the opposition if they ever want to get anything done.
Harper, time and again, has failed to do this and in a time of economic crisis he decided to try to cut funding to other parties instead of build a decent stimulus package. Since he only holds a minority of power it is up to him to keep the confidence of the house and he has failed to do so. A vote a non-confidence traditionally means the Governor General would look to the polls to make a new government however she already has a fresh idea of what we want and another election won't change that. After prorogue if Harper has failed to get the majority of confidence in the house the Governor General will have to go to the opposition who will have a party with enough confidence of the House to lead our country.
The majority of Canadians voted against Harper and with his power he refused to work with those we elected. Harper tried to do the same thing in 2000 and 2004 and even went as far as writing the Governor General asking her to consider a Bloc/Conservative coalition against the Liberals. Back in 2000 and 2004, Harper and the conservatives would have loved the Bloc vote at the time but now that they lost it they're acting like sore losers.