It was a fluke that the Habs had home ice in the first 3 rounds. It was a fluke that they played Hartford in the second round instead of the Nordiques. It was a fluke that they played the Rangers instead of the Flyers in the third round. It was a fluke that they played Calgary instead of Edmonton in the final.
Also, in the regular season, Patrick Roy was...
GP 47 W 23 L 18 T 3 GAA 3.36 SV% .875
In the playoffs he was...
GP 20 W 15 L 5 GAA 1.93 SV% .923
With the benefit of hindsight we can say that this type of elevation wasn't a fluke for Roy because he did repeat it in other playoff runs. But in 1986 it was a total and unexpected fluke of all flukes, even to Patrick himself, probably.