Many of the weird choices about that airport was made so it would be open and useful for the 1976 Olympics. The location was closer to Montreal (but father from Ottawa) in part to make the international arrival experience better for the fans (not for the long-term users of the airport). The plan was 'International flights in time for the Olympics and Domestic flights a couple of years later' as a way to 'show off to the world.'
All this rushing and purpose-building led to suboptimal decision making that ultimately made it a completely wasted investment.
A similar story can be told about Olympic stadium in Montreal.