Since Peter said that David didn't go to heaven, how is anybody else in heaven?

well he is dead and buried but david if your talking about the david and goliath david then yes he deserves hell he ended up betraying the army he fought with when he killed goliath then after betraying his best friend he then kills his friends father and then his best friend goes and wipes out the country of moab and kills all the men and sells the women and children as slaves then goes and kills more his ultimate goal was to rule the world he did not get to heaven