If I had to guess, I'd put it down to whereabouts in France you live. If you're in the south, it is probably more advantageous to learn Spanish or Italian as your first foreign language. Likewise German in the east/southeast.
Whereas Japan is really only focusing on English with something like 8 years of mandatory education now.
I'd also call into question the methodology used in determining competence in this study. I've found that French people will tend to have much better conversational English as the languages are quite similiar, whereas Japanese people can be quite shy and hesitant. If this study is conducted as a written test however, you could easily find the Japanese taking the lead.
France - the French have a very long history of feeling that the French language has a prestige status in the world. English is now a fairly large force in the world, but it wasn't always. Whether French is still a prestige/world language or not now, the French are incredibly proud of their language. The incentive to learn English, one of their languages largest competitors, is just not there.
I do not feel the last part of your statement is at all true. France is absolutely proud and protective of its language, but is trying very hard to teach English to its population.
France has mandatory English lessons. 7 years when I was going through my education, but I believe it's closer to 10 now - I know you can start English lessons at 8 but am not sure whether you have to.
Additionally, when I was going through higher education, it was next to impossible to avoid English lessons - that's easily another 3 to 5 years.
Put together, 20 years ago, I went through 11 years of English lessons through a fairly standard cursus, 7 of which mandatory. And as I said, it's gotten better (or worse, depending on your point of view) since then.
I'm not pretending that most French people have excellent English skills, but I do feel it's unfair to paint France as dragging its feet when it comes to learning foreign languages, English in particular.
Whereas Japan is really only focusing on English with something like 8 years of mandatory education now.
I'd also call into question the methodology used in determining competence in this study. I've found that French people will tend to have much better conversational English as the languages are quite similiar, whereas Japanese people can be quite shy and hesitant. If this study is conducted as a written test however, you could easily find the Japanese taking the lead.