Sorry but if you're blaming Gundogan for the goal then you literally don't have a fucking clue. This is really basic stuff.
Gundogan does exactly what he's supposed to do, after the first ball goes in, pushes up so that all of those Palace players are offside....or at least they would be if everyone did their job like Gundogan. Someone fucks up, and its the ginger bloke who is rooted to the floor staring at the ball and playing them all onside.
If you've looked at the replays to work out who is to blame and landed on Gundogan...go watch a different sport.