They are tricked by Satan to walk down the path of evil and darkness. They are praying homage to false idols, addictions and vices of the Earthly realm. They are pulled further away from their spiritual truth God wants his children to come home to him, to turn away from the evil lurk of Satan and his henchmen.
If he could find a child or children who were willing to write a book about a conversation between God and humanity explaining the truth of his love, it probably would be similar to the following dialogue. Humanity starts the conversation and God explaining his perspectives of why what he does to teach his children, because he loves all of his children.
No matter what awful transgressions they have or will commit in the past, present and the future, from murder, adultery, lying, stealing and deceiving others. No trangression is not forgivable.
When they are repented and called upon Jesus for mercy, admit their transgressions and accept the Salvation of coming closer to the Creator, then they are saved and are reborn as Children of God. The peace that comes with this sacrifice can not be describe in human language. Only by letting go of freewill will humankind understand the truth of the Messiah.