God not so mighty

       My question is, if God is this all mighty being, than why must he send others out to do his work and to spread is greatness. Shouldn't a God that is the only true god, allegedly,  be able to get followers because he is simply so great and powerful? Why must God convince people that he is great, and make others preach his greatness to get them to follow him. It never really made sense to me. I always thought that if something or someone is so great than others do not need to be convinced of it. They will simply believe it. Perhaps that is just naive.