Two different concerns:

1) business giants have a lot of money to hire the best. Startups need passion because they don't have a lot of money. Canada definitely needs more world class startups in many areas not just AI. 

2) the fact that these people will continue to affiliate with their universities, and will still be in Canada, allows growing of the cluster of expertise that creates passionate startups

Would it be better if they were working for a major Canadian firm yes. Would it be better if they simply stayed in academia, I don't think so.