Hm, weirdly, I had never really connected dungeon crawls JRPGs (Etrian Odyssey, some of the SMTs, etc) to the western CRPG blobbers, but I guess they’re pretty much the same genre, going back to the Wizardry roots. Etrian Odyssey is so much its own thing, and the mapping gimmick was so strong, that I never really thought about it, and SMT has the monster hunting thing.
I guess my point is, this appears to be a Spike Chunsoft game, so it didn’t come out of nowhere, per se, it has a provenance, which makes the success of the core loop less surprising.