League is small enough that looking per team, per goaltender season can make sense here.
Did not play that many games, only 3 in 1953, maybe in 1954, only 17 games but his 1.59 gaa was significantly lower than McNeil.
you have Harvey that could have entered his prime and in 1954 you have Beliveau starting to play has well, the teams could have been getting better in general gearing toward the dynastie.
Some possible other change around that time
1951-1952: Goaltender goal crease got bigger
1952-1953: Roster size change (15 on the road, 16 at home), from 17 + goaltender
1953-1954: roster now 16 + goaltenders
1954-1955: roster now 18 + goaltenders
Maybe smaller roster size those 2 season, played a role ?
But in 1953 if 5 teams allowed virtually the same amount of goals, looking at what happen for Chicago would probably be the way to go.