Honestly I don't remember any time when Japanese manga/anime/video games weren't popular.

90s kids grew up watching Dragon Ball & playing Metal Gear Solid and Super Mario 64.

Video games, yes, but anime (aside from a couple things that played on normal channels, like dragon ball—seeking out more, though...) and especially manga were things only certain kinds of dorks enjoyed, among those whose high school years were in the '90s and '00s. Toward the veeeeery end of the '00s (as the kids right behind that group started reaching high school) it was changing, and what's remarkable now is how entirely normal it is, even manga. It's no longer unusual for the popular kids to like it.

It was kinda hard to even get anime in that time period, if it wasn't one of the few played on TV. Hell, even US TV shows had only recently started coming out as complete DVD sets, most still weren't available that way, and publishers were all over the place on what they thought a season was worth. You pretty much had to be into Internet piracy to be a fan, or know someone who was and would get stuff for you.