Why Islam was so successful?
Islam is not the only successful monotheistic religion to come from the Middle East. However, Judaism and Christianity each took centuries to form and succeed, whereas Islam benefited from the Judo-Christian traditions and became an enduring empire of the mind and the land within 30 years. The empires of Attila the Hun and Genghis Khan also captured huge countries in one lifetime, but none of the Hun and Mongol empires have survived as a global ideology and civilization.
This success despite starting from the arid and poor land of Arabia, where the early Muslims in Medina did not even have picks and shovels to dig a defensive trench (Khandagh) and had to borrow from the neighboring Jewish tribes!
This despite the general intellectual and cultural backwardness of Arabs in Mecca and Medina, who were mostly illiterate (Jahel) with even the prophet Muhammad incapable of reading and writing. Therefore, most of initial scribes of Koran were from the enslaved Jews!
And despite having to fight the two great empires of Persia and Rome, right from the start!
Compared to the convoluted Jewish rituals (600+ commandments) and the complex Christian theology (Trinity of Father, Son and Holy Ghost), Islam is very simple to accept (testifying that there is only one god, Allah and Muhammad his last prophet). It is easy to understand (the Surah of Hamd as key to Koran … praise Allah who is kind, and obey him to be saved).
2. Stick and carrot
Also, the promise (paradise) and threat (hell) of afterlife, makes the Islamic ethos easier to understand and to follow (this world is a big testing arena and god is watching your every move … if you do as you are told, you will get benefits both in this world and the next). This in comparison to Judaism that had no afterlife, and Christianity that denied this world’s pleasures.
3. Militant energy
Jihad is at the center of Islam, historically and practically (Hitler was impressed by Islam's vigor). It has never been a religion for peaceful spirituality (even Rumi was a Jihadist) and is best suited as a warrior cult. It assures the Muslim fighters of their success, whether they win (worldly pleasures from looting and raping) or lose (paradise with 70 virgins). It completely unburdens the Muslim warriors of any code of ethics and “chivalry”, when dealing with the infidel enemies. From the start in Medina when dealing with the Jewish tribes (using mass murder, enslavement and rape of women) to Mecca when dealing with infidel Arabs (using treachery and oath breaking), the Muslim Jihadists could do no “wrong”.
So how come Islam has not conquered the world?
Islam has been very successful against many opponents but has had its limitations too.
1. Lack of artistic imagination (forbidding the painting, sculpture, music, singing, theater …) as rooted in the brutish Arab Sahara culture. This has limited Muslims’ creativity and versatility, as most innovations and much progress is rooted in arts and the flight of imagination.
2. Incompatibility with post-renaissance science and knowledge, and inability to change and adapt to the changing ways of the world. Islam means submission and as such is most suited to slave-holding societies like the Abbasid dynasty and the Ottoman empire.
3. Islam has been unattractive to the artists and scientists who have changed the world since the peak of the Ottoman, Persian and Mogul empires in the 1600 CE. Intelligent free-thinkers and inventors do not get attracted to Islam, but unfortunately, retards and radicals do.
Reference: Muhammad, his life based on the earliest sources, by Dr. Martin Lings