Hockey has a significant amount of randomness due to the sheer complexity of the game; the greater the number of factors you introduce into producing an outcome the greater impact of randomness in any outcome. A game played on ice that gets chewed up over time, with a rubber puck that can move unexpectedly, sticks that can break, skate blades that get nicked, boards that can produce uncertain bounces - then add in the randomness of the players' and officials' health/perception on any given night - and there is a lot of 'chance' involved in hockey. Over time of course, most of these factors even out a fair bit and become less influential, but there is a lot of randomness in hockey, especially in any given game.
In my view, it makes it more exciting - hockey has a great blend of chance and skill. Skilled response to randomness is what's interesting, for me anyway. And, this does not take away from the champions at all, winning the Cup is extremely difficult because of the complexity of the game - and over time randomness has a tendency to become less important.