Athletic Bilbao did much more than I expected from them. They simply destroyed Atletico Madrid by 3-0 home as well.
But I can't say they didn't deserve because Atletico Madrid were really not good enough in both games. 
Having an important player missing like Griezmann also made a bad impact on their performance last night.Now the name of the finale in the Copa del Rey is Athletic Bilbao - Mallorca. This is going to be a really unexpected kind of finale. As far as I know Mallorca won the cup once many years ago but I don't remember any when it comes to Athletic Bilbao. I hope Athletic Bilbao manage to be champions.
And in place of Mallorca there could be Girona. ) I agree the final is unexpected, and it seems to me that Athletic will be the favorite in this final. They are looking very good now, they beat Barcelona and Atlético Madrid on the way to the final, I think this fact already shows how strong this team is now. By the way, Athletic Bilbao is quite close to the top 4, they are only three points from Atletico and if they can continue and play so well, then they have a very good chance of trying to get past them.