We can't judge Sevilla about their place in La Liga because they didn't focus on the league games and they didn't need the La Liga games to earn points at all in the last games because they couldn't reach the top of the table and on the other hand, Sevilla wanted to win the Europa League and they have enough hope for it because of the last wins the had in Europa League.
In the end this is true and Real Madrid was trying the same. They wanted to make the La Liga season be forgotten by the win of the Champions League title and it would have worked. Nobody would be talking about their inferior performance compared to Barcelona had they won the Champions League. Of course everyone knows that Sevilla didn't perform well in La Liga, but of what help is that to Manchester United and Juventus Turin?
Both of those clubs saw that Sevilla is struggling in La Liga, but that had obviously no influence on the game against Sevilla in the Europa League. Even when sometimes it is hard to understand, it is still two different competitions and it seems that a team can show two different performances.