I live in the Netherlands, I can explain why so many Dutch people speak English here fluently.
We have a lot of television, games and other multimedia here not being translated to Dutch.
TV gets subtitled, but audio remains English.
This way children get adapted to the language early on, even though more cartoons and games get dubbed these days.
But even then, Dutch Wikipedia pages usually contain little information compared to their English counterparts, a lot of stuff found on Google is unavailable in Dutch (especially tech-related things), those are factors that make English a crucial part of the lifes of older people too.
Looking at our huge neighbour: Germany.
Everything must be translated or dubbed to German before anyone gets their hands on anything.
As a result, a lot of Germans can only speak German, even though the English lessons at school are equal to the English lessons here.
I don't know about Scandinavia and Iceland, but I expect them to have similar reasons to the Dutch.
