why did they screw up the Percy Jackson movie so much?

so i know this question has been asked a lot, but i am just so
outraged i will say it again. WHY DID THEY MESS UP THE PERCY JACKSON
MOVIE SO MUCH!?!?!? I mean really, almost urgently they messed things
up. So why!?!? the books were amazing. why did they change so much
for no reason?!? i guess i understand it a little, but little things
like percy not being in bording school and hades being like some weird
demon thingy. its bull crap!!!