2) The Tales series reached a saturation point where new main games don't reach the whole Tales fanbase anymore due to fatigue while new all-inclusive fan servicing games like this one still do.
That's an intriguing theory that might have some real weight to it. Have Japanese fans finally grown so tired of the storm of new Tales games that they would rather take refuge with older, familiar characters? On one hand, it seems viable, but on the other hand, you would expect ToS:KoR to have done better in Japan if that was the case...