It's not that hard to comprehend the massive success of mangas & animes in western countries, especially compared to the (rather lack of) competition from the western entertainment media in recent years.
Mangas and animes are very easy to access and share through Internet, and with new content that appear generally in a weekly schedule. The huge amount of productivity is a part of the appeal for consumers and while a lot of japanese trash is created, there is still a consequent number of good stuff too.
France in particular, despite known as a big industry of quality comics in the past (Asterix, Spirou, Tintin, Smurfs, Troy, etc), has seen at least half its market dominated by mangas because their volumes are much cheaper to buy for the average person than franco-belgian comics. We're talking about a manga costing around 6€-8€ versus a 15€-20€ french comic of 48 colored pages, in a country where it's completely forbidden to cut the prices of books by more than 10% off during sales. Admittedly, France is an exceptional case because japonism has been a thing for a very long time (its been amplified by TV anime in the 70s) thus is much stronger among frogs than anywhere else, but still.