One of the greatest postseason pitching teams ever was the 2001 Diamondbacks. Now, in the end, they won. However, they barely won in the first round, and, in a way, the 2001 World Series speaks to how much of a crapshoot the postseason can be.
The Diamondbacks dominated that entire series, yet they went back home down 3-2 because their closer made two bad pitches. In the end, they won, but it was literally thanks to the absolute slimmest of margins. Even though they dominated the entire series, they only won thanks to two huge mistakes by the Yankees in that bottom of the ninth inning.
Very similar to the 1960 World Series. The Yankees dominated the Pirates in almost every statistical category, and were clearly the better team, but ended up losing the series.
It can be very flukey.