> Is anime & JAV to blame here?

Yes, people are going to be interested in a culture based on its cultural exports and Japan punches way above its weight in terms of cultural exports. And it's not just anime and JAV, it's also literature and music. Having content that you want to consume will make it easier to get motivated and to stay motivated. On top of that intermediate and advanced language learning is, to a large extent, driven by media consumption so the availability of a large amount of interesting content simply makes Japanese easier to learn than many other languages.

This is also how nearly everyone learns English.

When China will start exporting interesting content more people will want to learn Chinese and succeed in learning it.