The killer dripped blood from the left side of his body as he left the scene. Did the police sneak into OJ's house and inflict a deep cut on his left hand finger? The killer wore extremely rare size 12 Bruno Magli shoes. Did the police sneak into OJ's closet, take the shoes, and return to the crime scene to plant the shoe prints? OJ denied he owned such shoes but photos later surfaced of him wearing them.
I could go on and on. He should have been easily convicted even if there were no blood evidence. So no, it's not more complicated than people believing bullshit.