#3 Jose Mourinho erred in starting defensively
The Portuguese manager has earned plenty of plaudits for his tactical nous over the years, most recently when Mourinho started with a defensive block against the effusive youth of Ajax in the 2016/17 UEFA Europa League final. It worked brilliantly, as United's experience resulted in a comfortable 2-0 win.
Real Madrid are far cannier though - Zinedine Zidane anticipated Mourinho's 3 man defence, and started with a diamond, thus ensuring that Los Blancos dominated the wings. The space Dani Carvajal was afforded to make his pass for the first goal would be criminal by Jose's standards, and he rejigged his transitional shape in the second half, bringing on Marcus Rashford and Marouane Fellaini.
The pair made United look far better, with the Red Devils troubling Navas far more often. Perhaps Mourinho needs to have more faith in his team, and begin games on the offensive because big teams in the UEFA Champions League will take full advantage of a head-start.