I think it doesn't have anything to do with luck that Sevilla won the Europa League title. Actually yes at first they looked really lucky in some matches. Because they weren't still able to improve their performance due to having a bad season. Their luck helped them until the end of the first leg against Manchester United. But as of the second leg we have started to watch a really different Sevilla. They finally started to play as they should and we started watching the usual Sevilla again.
As of that date Sevilla deserved to eliminate every single one of their opponents remaining in the tournament. In the finale they deserved it again because of showing a great performance at using penalties. They become something different when it comes to the Europa League even if they perform badly in the La Liga.
With the conditions of the champions and the good job they did from the quarter finals to becoming champions now it's not suitable to say that they are just lucky in this regard.
This case is the same as what many people said about Madrid last season and I'm actually quite ambiguous about this because that's why some of us always say that clubs that are not too favorite to win are always said to be lucky even though they are also trying hard for it.