He wanted to test Adam and Eve, and let them have a choice. Either they could be selfish and keep paradise all to themselves, or they could give up paradise and let us be born into mortality, with free will to choose for ourselves. God created humans, and humans should have agency. He was testing out his creation to see if it would work properly, and it did. Thanks to Adam and Eve, we have the ability to choose for ourselves, and the whole meaning of life is to see if we would still be faithful to God, even in this imperfect world. If we never had the ability to choose, we could never get to heaven and be stuck in the pre-mortal world forever, and never obtain true happiness.