cuz if joker just died in the beginning would he really have to fight god n stress the general public's life having them be scared of super beings having the control to steal hearts?
heh it would've been convenient for the phantom thieves to fix criminals and stuff, just without the whole website or notoriety. Imagine all they did was change hearts and had 0 exposure, the police would just find it mysterious and the general public wouldn't have to consider mysterious forces. But of course, we wouldn't have this brilliant site without all that, or a great game.
