I take your point about videogames as ingress in jp music. This wasn’t my experience, but I would imagine that a ton of vg soundtrack looped back to YMO, and that some of the big early-mid 2000s soundtrack games like jet set and katamari drew people in.
As a young music obsessive rather than very interested in games at that time, the points of entry in jp music I recall were
A) metal/heavy psych like Boris, High Rise, les raillez desnudes, acid mothers
B) the real mutant stuff like merzbow, gerogeri, keiji haino etc
This was available in record stores, no resorting to file sharing needed. Obviously this was in the context of hyper-snob record store filtering, at least where I was. So I mean it was somewhat available
There were also a few notable collaborations that got some traction: john zorn with a number of japanese (+thai, vietnamese, and other regional musicians), cibo matto did that album with jon spencer, and I think the big one (relatively speaking) was faye wong + cocteau twins (not japanese I know, I’m not racist)
point being that if you were already part of the serious music culture, there were analogue connections. THAT SAID, I think you may be right that internet sharing/uploading really expanded access to jp music. Access was heavily gated by the whims of the weirdo boutique and bootleg labels that would press music from categories A and B and trickle them out to record stores, in which older and smellier dudes would almost always buy them first
So speaking for myself I’ve found exponentially more interesting jp music just bouncing around youtube than I had in record stores and on blogs