The Abbasid dynasty hosted a very important reform that made possible a lot of the literary and scientific advances of the next two centuries: they reformed the writing system.
The Semitic language family has been around as long as written history, in various forms: Aramaic, Hebrew, Assyrian, Phoenician, Ugaritic, Amharic and Arabic. The early books of Bible history make more sense when you realize that the Moabites, Amorites, Edomites, Canaanites, Assyrians, Babylonians, Akkadians, Chaldeans, Arameans and even Ethiopians could understand each other if they really needed to. (The language of Sumer was not related.) The Akkadian language developed cuneiform, which became the universal writing system of the ancient world. At the same time, Phoenicians developed their crude alphabet, which influenced both Hebrew and Greek. The early system of Semitic writing only noted consonants, since grammar stipulated the vowels.
The Southern desert branch of the language family wasn’t written down until last. There are only a few pre-Islamic documents to indicate that Arabic had borrowed an Aramaic script. Literacy was just not an issue, another reason to think that Mohammed did not read or write. When his Companions assembled the Koran and hadiths, they were still using a cobbled-together script that worked only reasonably well for Arabic. It was hard to learn and hard to read, another reason why Koran memorization became an early tradition.
During the Abbasid Caliphate’s Golden Age, the Arabic script was reformed. The Abbasids moved their capital from Damascus, a Semitic (Aramaic) center, to Baghdad in Persia. This meant that Arabic was, for the first time, formally studied as a second language by people with a completely different (Indo-European) background. In Baghdad, a linguist known as al-Farahidi began to update and reform Arabic writing. His goal was to standardize writing for poetry, and he also wrote a dictionary.
The chief reform was to use a simpler vowel marking system. There had been experiments with using dots over and under the flowing consonants, sometimes with different color. Al-Farahidi worked out a simpler way, and he also added an extra consonant.
Al-Farahidi’s patches on the system made it possible to actually read Arabic without being a Bedouin. The enormous effort put into translation in Baghdad was only possible because they now had a workable writing system. Eventually, the Koran was rewritten with the new system. Persian, before written with cuneiform, moved to the Arabic script. When the Turks began to invade and gradually got converted to Islam, their languages were first written in it, too. Eventually, all eminent scholars had to know the Arabic script.