Playing seriously or not but losing with a score of 4-0 is still a shame, because even though England didn't play seriously but at least with their status as a big team and they also have a big league too. So, even if they didn't play seriously they could at least hold on to a draw or lose by a narrow score, what's more, England's one red card made it look even worse. At least when the big teams are trying and or preparing a strategy for the world cup, they can still play well, ending the match with a draw and or losing with a close score of course it will be more respectable.
The Nations League Cup is an official FIFA competition, which gives points for ranking. A team below the ranking beats a team far above the ranking, allows you to earn a lot of points.
Of course, England wanted to win, but they faced the game extremely easily, and ended up suffering a heavy defeat, in an official competition and not in a friendly one.