From the videos of the landing, my initial armchair guess is they got some wind shear or strong gust at just the wrong moment, which caused a quick drop and slight roll to the right. The right main gear touched down first, very hard, and broke. The right wing then snapped as all the weight came down on it.
Bink63
It's possible the "bump" the controller mentioned could have unrelated to wake turbulence from the plane that landed before it (though that was my initial thought) but instead referring to the ILS glide path. The ILS system is very sensitive to objects being near the antennas. So another aircraft or even vehicle passing close to the ILS antennas can cause the signal to get affected in a way that the glide path the plane is following deviates up or down briefly. Pilots are aware of this and autopilots are designed to handle it (though this close to the ground they should have been hand flying so no autopilot). So if that's what the controller was referring to, this would not have been a factor. Even wake turbulence is unlikely unless the previous aircraft had touched down withing the last 30 seconds or so (unlikely as there is more than that as standard spacing). An exception could be if the previous flight landed much further down the runway, as then the wake turbulence would have started higher up at the point the CRJ was landing, and could still have been forceful when the CRJ was flaring.
Toronto has had some great luck though. The last major airline crash there was the air France one almost 20yrs ago that went off the runway and caught fire. It also had no loss of life.