yeah, its v. confusing.
this is my theory:
thousands of years ago, the sipirit, if u will, of the keyblade made thousands of keyblades and gave them out freely. but light cannot ,and willnot, exist without darkness. the darkness in peoples hearts manefested as the searched for more power.the people figured that if they could beat the other keyblade weilders, they could be all powerfull. thus they slaughtered each other. prehaps the 'chasers' are the only ones that did not join the struggle for power.

if u guys think this is wrong, feel free to scold me and corect me !!!