(Besides Anime)

It’s pretty much entirely because anime (and adjacent content). You can’t exclude that and expect a coherent answer.

People learn languages when they have a cultural reason to do so – such as engaging with media in that language or wanting to interact with people who speak it (for business/relationships/diplomacy/whatever).

Hollywood movies and rock-and-roll were big drivers that pushed people to learn English last century. Programming and the internet probably pushed a bunch of people to learn it in the last ~20 years. K-Pop and K-Drama have been drivers for learning Korean recently. German was one of the major languages (along with French) for math and science before WWI – but was overtaken by English after that. You get the picture, I hope.

If the US continues on its current path, maybe in a few decades all the new research papers coming out will be in Chinese instead and everyone will learn Mandarin to discuss new tech. 🤷️