A mix of St-Louis being not that good during his peak and Hasek in 1999 when he was on a big market, good team maybe...
92-94
Blues were allowing 39 shots a games in the playoff, shooting only 30, regular seasons it was 34.2 to 29.8, close to the worst among non expension teams...
Which for his battlers capacity-style the blues were maybe perfect to shine and made him a first round playoff heroes, but did not made it easy to win Vezina in that era, it was still pre save percentage is king days.
the 92-94 Blues with competent replacement goaltending (Guy Hebert was a perfectly capable number 2)
Joseph: .911, 3.04, 92W-71L-30T
Others: .883, 3.86, 21W-31L-3T
League average was .890. He would not have been a bad Vezina winner during that peak or Hart candidate, it was a really massive improvement over competent replacement.
Roy-Belfour-Hasek won those years.... 1999 was maybe Hasek best season of his career (and I am not sure how much of a better season than belfour-brodeur-khabibulin-Roy he had that year)...