Because that's football, luck is a big part of the game. That's how Real, for instance, won multiple consecutive UCLs! Special goals and slices of luck carried them all the way to glory again.
Luck and Messi are carrying us this season.
What is a similarity between that Real and Barca this year?
None of them are playing too attacking, naive football.
Both of them had good defenses.
And both of them had 1 magician upfront who will make a difference.
That's the state of top football in the last 5 years.
France in 2018, Germany in 2014, Chile on Copa Americas, Portugal in 2016, Real 4 times in 5 years, hopefully Barca this season.
Every single of these teams played:
1. cautious
2. not overly possession based football
3. they don't keep possession at all costs and these teams will always boot the ball upfield. You need to minimize risks around your box (what Pep's teams aren't doing).
4. and you will just win titles since you will make LESS DEADLY MISTAKES than your opponents, and/or you have Messi/CR7/Mbappe upfront to grasp 1:0 victories
Knockout matches in the last 7-8 years have turned into:
= MINIMIZE your risks and outwait and outsmart the opponent and wait for his mistakes.
And this crappy type of football is a type with which France won a World cup, how Portugal won Euros, and how Real won their titles, isn't it?
Days where crazy possession game with 10 players in the opponent's half and where you are prone to counters whenever you lose the ball was a winning tactics=are gone.
Look at the results of Spain NT in the last few years and of Pep's teams in Europe.
They can't do shit against more cautious, counterattacking teams.