It sort of makes sense almost, this is about when Japan idol mania reached an all time high as far as music deals were going (Kingdom Hearts, Final Fantasy X-2, Phantom Crash, etc.). Fortunately Sega would go waaaaaaay underground for the music for MadWorld and Anarchy Reigns.
Still among my all-time favourites. Ironically, the Otogi games seem probably more relevant now than they were back in the day, because of how they completely contravene almost any mechanical cornerstone of the character action genre, and also anticipated some of the slow, methodical combat that made the Souls games popular.
I agree that no one has really done an in depth exploration into how every aspect of King's Field was broken up into different games by From in the early 00s. Shadow Tower, Eternal Ring, Otogi, and KF The Ancient City's concepts and structure all coalesced back together to form the ultimate game, Demon's Souls and its wonderful successors.
Shadow Tower - In a towering nexus to warp to different realms, no classes or traditional leveling up, you upgrade items with demon's souls. No in-game music outside of special moments.
Otogi - Teleport into discrete levels all over the kingdom like in Demon's Souls, weapon weight has a subtle effect on jumping/etc. Consistently foreboding and dangerous atmosphere compared to previous From games.
Eternal Ring - RINGS!!!!! You could say From Software really "clings" to having lots of rings now! Heal up by eating tons of grass.
KF: The Ancient City - Weapons/etc. can be upgraded with stone shards by a blacksmith which would become a huge part of Demon's/Dark Souls. Setting starts out like typical fantasy but areas and enemies gradually becomes more Lovecraftian as the game goes on.
It's particularly amusing when you look at how Otogi got largely sneered at by hardcore fans of Ninja Gaiden and other twitch-skill hack 'n' slash titles, but nowadays the same kind of elitist filth intoxicates large amounts of the Souls community.