Because the conversion of a king followed by his people would be based not upon reasoned thought, intellect, but following the crowd. Then you can get them to do anything like a ritual prayer, bowing down to God when they are used to bowing down to the king, etc.
When they do not understand what and why they are doing something, then it is easy for the kings, priests and capitalists to exploit them.
Keep them busy with rituals and make heaven their goal, not a heavenly earth based upon what the Qur'an says.
No consensus? Then judge from the Qur'an not natural laws in ilm this or ilm that!