Principle number 12 of Basic Elements of Islam: You must read the Quran in Arabic. This unites believers by language, and language has a very powerful unifying influence. For added incentive to learn Arabic, another basic Islamic principle says you can't go to Paradise unless you pray in Arabic.
So Muslims all over the world share a language. This makes it easier to coordinate far-reaching campaigns of protest, political pressure, and war. Read more about this principle.