Demidov and Michkov both would have given us firepower equal to '70s hey days. Reinbacher solid piece but you can get them in UFA. ie. Pesce or Montour types. Michkov predicted 100 points, you just can't acquire them.
The upside is clear but with Michkov his physical and athletic profile gives cause for concern whereas for Reinbacher his physical and athletic profile seems optimal for the NHL. Then when you view their abilities and skills and performance in their draft year, Reinbacher doesn't look out of place next to Michkov. So in the end the Habs went for 1) position of need, 2) more successful-looking profile (risk management), and 3) the player they wanted at 5OA all along.
If Will Smith was available I'm not sure Reinbacher would be a Hab but Michkov was not on their radar at 5OA.
As for Demidov, I'm not sure what he can get to but every hype video just adds more hype. I really hope he succeeds, it would be so wonderful.