Who said they were being gotten out randomly? Of course teams lose and win for a reason. I've used the term randomness - but I should have restated it ... it's noise in the data.
Put another way - since you brought up gambling - there is no doubt that Phil Ivey (or whatever famous poker player you want) is a better poker player than me. If we played a ton of hands, he'd clobber me (assuming I had not busted out by then). But - I'm going to run into a few wins here and there. It might be because he makes a mistake (since he is not perfect), or I make a mistake (since I do at least know something about poker), but most likely it's because you play the percentages but the cards went my way. In horse racing, the long shot only has to win the race once.
Given the nature of baseball (the rotating pitchers in particular) - a best of 5/7 is not much more certain (if at all) than single elimination. There is just a lot of variability - much more than any other sport's playoffs. In the micro, there are specific reasons (of course there are) why any single event occurs. There will never be a Super Bowl III in the baseball playoffs.