Mohammad, by contrast, in the process of turning the world into a Muslim state, has been responsible for the deaths of 270 million people.
Regardless of how much territory previous conquerors have seized, how many people today are followers of Napoleon or Hannibal or Genghis Khan? But how many people today are followers of the seventh-century warlord, Mohammad? More people than those rulers could have imagined.
Right now, Islam is the largest nation in the world. China's population is 1,338,612,968 (source). The world Muslim population is 1,519,747,019 (source).
As it says in The Terrifying Brilliance of Islam:
10. Islam must be your first allegiance. This is a great idea to add to the collection if the goal is world domination. You are a Muslim first, before any allegiance you give to your family, your tribe, or your country.
This does two things: It causes a unity of people across borders which allows the group to grow bigger than any other entity. In other words, the "Nation of Islam" can grow bigger than any country, no matter how large (which gives the group a massive numerical advantage).