Have you ever flipped a coin? If you flipped a coin without ever taking a statistics class or doing it by hand and predicted the result, the end result usually looks something like this: T, H, H, T, H, T, H, T, etc. Our minds know that the probabilities is 50% so if you wrote it down without trying it or understanding how statics work, you assume in a hundred coin flips it must be close and we force a state of fairness onto the coin.
In reality, it works closer to having a bunch of heads or tails keep popping up and the more times you flip the coin the closer you are to the 50/50 mark. When this applies to a game though you only flip it once. Hence upsets happen. No matter how stacked the odds, eventually the underdog will win no matter how bad the odds. That’s how reality and competition works.
That’s why we play out tournaments and that’s why upsets happen. So when an underdog does upset the better team, suck it up. That isn’t reality cheating you, that’s just reality being reality.
Our very existences are all technically statistical impossibilities so your favorite team losing isn’t some wild never before seen circumstance.