Really weird result, Bilbao the better team in both ties but ended up losing badly
Yeah they played United off the park for 70 minutes at Old Trafford, but United freshened things up, scored on the night, and the Athletic players' heads dropped.
Lindelof really should have been sent off for a shin lunging tackle at 1-0 too. That could have changed everything. United have had a lot of lucky breaks in Europe this season with officials.
As you say, Athletic were the better team in both legs, particularly the second, but lost heavily. 7-1 on aggregate is really harsh for how they performed, especially in the second game.