If the Joker wanted to really shake up society, he did not have to go through elaborate plans of planting multiple bombs and handing out detonators. He did not have to burn piles of money or kill politicians. All he needed to do was burn a couple of Korans and the Religion of Peace would be sure to engage in general lawlessness and chaos. Even the politicians would go crazy with rage.
Maybe the Joker was scared of being beheaded? After all, Batman doesn’t behead people.