Once a long time ago we all lived at home in heaven
Hence step by step we descended deeper and deeper, more and more away from heaven until we ended on earth.
God - our all father - still loving us but we unable to live in love and peace with all our friends, brothers and sisters - we decided to benefit from each other, to cheat on each other, to lie or even to kill ...
Hence we now are so much separated from being a truly loving person that living in one world, together with Billions of others would instantly cause us to destroy again all heaven - hence we would instantly fall again down to hell on earth.
Only true love can heal all wounds we all have created on Millions of others. Here on earth we need to prove for a full lifetime or beyond any doubt our maturity to do so.