TVA Sports reporter Anthony Martineau spoke with a Montreal Canadiens scout recently. As a result of this discussion, we now know why the CH selected Juraj Slafkovsky and Filip Mesar in the first round.
According to the scout in question, it's because of their many qualities, obviously, but mostly because of how close they are to playing in the NHL.
Finally, this same source mentioned to Martineau that the first overall pick, Juraj Slafkovsky, would be very close to the NHL, mostly because of his physicality.