Indeed, that came up, and continues to. When the project began, it was Bitcoin mining, now it's AI datacentres. Both of them are better suited to the infrastructure: less demand in winter (cooling), and willingness to locate those megastructures up north, close to the dams (no expensive-to-build, expensive-to-maintain transportation, away from farm lands).
It comes down to this: politics, finer: diplomatic soft power. Once the northern States become dependant of Canadian electricity... how about some counter-tariffs? Ask yourself this: why sell more to the US than to Ontario?