An ancient analogy:
A garden is surrounded by a fence and the evil beasts are outside.
Man’s job is to watch over the garden and to patrol the fence so the wild beasts do not enter.
But once the fence is broken and the evil penetrates, his task is to fight the beasts, both those already in the garden and those outside trying to enter.
Were the man permitted to make his escape, the garden would be abandoned and go to ruin.
Hence man is not so easily allowed to get out of his responsibility.
He has to stay on earth, continue to care for the garden, and try to get rid of the evil he has himself introduced.
–Rabbi Adin Steinsaltz