Barcelona were arguably the better team for the first 45 minutes but Bayern massively improved after the break, quickly scoring two goals.
Jon Mackenzie of The Athletic puts it down to a tactical switch made by Julian Nagelsmann at the break. Bayern's head coach replaced Marcel Sabitzer with Leon Goretzka, a change that changed everything in the game dynamics.
Here's the breakdown of the key ideas.
Bayern's 1st half tactic
Bayern started the game attacking through the middle. They are direct and create their chances by dominating the opponent and finding spaces in behind with Sadio Mane, Musiala and Thomas Muller ready to pounce.
To get the ball in the first place, Bayern's idea in the first half was to press Barca through the middle, win the ball high up the pitch and hurt Barca with their strikers.
Bayern commit men forward down the middle which creates lots of chaos in central areas and opportunities to win the ball.
Xavi's counter tactic
Xavi knew Nagelsmann's tactic from the outset so he set out his team to be aggressive when out of possession and to press Bayern high up the pitch.
Which such aggressive press from Barca, Bayern were prevented from dominating Barca's midfield. Their forwards, Musiala and Muller were also left isolated with Christensen and Kounde - two men who are considerably bigger and better in the air.
Barca's aggressive press high up the pitch isolates Musiala and Muller.
Nagelsmann tweaks things to beat Xavi
Nagelsmann knew he had been found out so he switched things up a bit in the second half. He replaced Sabitzer with Goretzka and instructed his forwards to move towards the wide areas and drag Barca defenders out of position to create spaces in behind. Xavi didn't see that coming.
With the likes of Sane and Mane dropping to the wings, Barca became stretched and that opened up spaces in the middle for Bayern to exploit.
Bayern forwards (Mane, Sane and Musiala) moving wide and dragging Barca defenders towards them.
Another problem was that Barca midfielders - Busquets and Gavi seemed to take their foot off the gas in terms of pressing Bayern as aggressively as they did in the first half.
The bottom line is that Nagelsmann's tweak worked like a charm as Bayern had more joy through the middle in the second period.
Before long Musiala found that space to create an opening for Sane and that resulted in the second goal.
Have a look at the tactical breakdown in full:
