The story was that Habs had a deal with Anaheim that included the 21st pick (and obviously other elements). It was only after Demidov was available when they were picking 5th that they decided to keep the 21st pick, which was also where they targeted Hage.
So basically it was
Option A: if Demidov is still up at 5th, we take him + we hope Hage is there at 21st (which they probably had another guy or two in that range to take).
Option B: if Demidov is gone, we take someone else we value at 5th or move back a few spots + trade 21st for Zegras.
If what Gascon reported is accurate, the Habs were walking out of the draft with either Demidov or Zegras.