In His work of creation, God had a problem with evil Beings*; because Beings cannot be destroyed, therefore evil cannot be destroyed. Nor can evil be confined because spirits cannot be confined.
Therefore, as soon as there existed demons - unincarnated spirits who are committed to evil; and also the post-mortal spirits of evil-serving Men; then these could not be eradicated.
(Some may repent - but what of those who do not?)
Because God could not exclude evil from all of reality; therefore, God needed to make a separate and wholly Good place - a place free from evil: in other words, Heaven.
Heaven is a situation without evil, because it is not a 'place', but more like the eternal alliance of Good hearts.
Heaven is possible when Men can make a transformative and permanent commitment to love God and work in harmony with His divine creation, and to love all other Beings that do the same.
To make Heaven therefore required that transformative and permanent commitment to Good which is resurrection; and resurrection required Jesus Christ: therefore Heaven did not exist until after Jesus had done the necessary work to enable Men to follow him through resurrection to Heaven.
Evil is an ineradicable fact of reality; and Heaven is not the exclusion of evil Beings from a place - but the exclusion of evil motivations from a Being.
