While the politicians played a part in where it ended up, it was mostly due to the Maroun family (owners of the Ambassador Bridge) buying up most of the industrial land around the current bridge and not wanting a new bridge to be built.
There is an added benefit of it getting a lot of the truck traffic out of neighborhoods in Detroit and Windsor also.
How a private business is allowed to own/control an international crossing like that is beyond me. My family moved here when my Grandfather came here to work on the existing bridge. Not sure who owned it back then.