On a serious note, why didn't Joaquin Phoenix kill Russel Crowe? It is the sovereigns dilemma.
The story of the bible goes as to explain a rebellion, a challenge to the sovereign. The people chose the rebellion, so the god allowed the challenge to play out, with the caveat that it would be temporary. Once the challenge ultimately failed the god would restore order and the challenge could never be made again.
The story is putative, and the actions of the supposed god are up to you to evaluate. Plotlines are easier to follow when you read the book.