The written compilation process did not take place during the prophet's time as revelations were an ongoing process. Manuscripts were not generated clearly earlier in his time. However, it was still recorded in bits and pieces.
From a historian point of view, citing islamic written material as reliable is difficult based on the theory that the complete compilation of the Quran was only seen in the 8th century, a century after Muhammad's death . Historical evidences (Historical Archaeology method) are evaluated based on textual sources: inscriptions, archival documents, narrative histories, law codes and guidebooks that support the main source (Quran in this example).
In the Muqaddimah, Ibn Khaldun warned of seven mistakes that he thought that historians regularly committed. In this criticism, he approached the past as strange and in need of interpretation. The originality of Ibn Khaldun was to claim that the cultural difference of another age must govern the evaluation of relevant historical material, to distinguish the principles according to which it might be possible to attempt the evaluation, and lastly, to feel the need for experience, in addition to rational principles, in order to assess a culture of the past. Ibn Khaldun often criticized "idle superstition and uncritical acceptance of historical data." As a result, he introduced a scientific method to the study of history, which was considered something "new to his age", and he often referred to it as his "new science", now associated with historiography. His historical method also laid the groundwork for the observation of the role of state, communication, propaganda and systematic bias in history, and he is thus considered to be the "father of historiography" or the "father of the philosophy of history".
With that said, the scientific method of historical manuscripts as evidences alone are not suitable for the compilation of the complete quran as you must understand that the arabs at the time did not have any paper. Paper, originally, was brought by the Muslims from China.
"It followed the battle of Tallas (751) fought between Chinese and Muslims, when Chinese prisoners revealed the secret of papermaking to the Muslims. From an art, the Muslims developed it into a major industry."
Location of the Quranic material included parchments, scapula, leafstalks of date palms and from the memories of men. Thus most of the written items before the Quran had disintegrated with time. In addition, it was discouraged to make coins or any form of adornments related to the prophet as it may mislead people to worship him instead. The difference in culture and civilization and limited access to academic tools like paper contributed to the little amount of manuscripts available. "Before the Quran was commonly available in written form, speaking it from memory prevailed as the mode of teaching it to others. The practice of memorizing the whole Quran is still practiced among Muslims. Millions of people have memorized the entire Quran in its original Arabic. This fact, taken in the context of 7th-century Arabia, was not an extraordinary feat. People of that time had a penchant for recited poetry and had developed their skills in memorization to a remarkable degree. Events and competitions that featured the recitation of elaborate poetry were of great interest".
What sets the quran apart from this was that, interpretation was strictly excluded to retain the purity of the material. People may then relate to the hadith for the majority agreed interpretation if they could not understand properly. In a way the Quran is unique in that it is the only source of its own with any sources before it to be of little importance as every detail were confirmed and recorded in the Quran. Further interpretation are to be based on human judgement or tradition in a separate book, thus preventing the corruption of the intended material. Interpretation is subjective depending on the person's level of experience, intellect and understanding.It is understandable if people discredit its credibility but it is important to understand the lack of writing technology that contributed to the late written entry of the Quran, hadith etc. Nevertheless, the practice of standardization had to be commended for it ensured that there is a clear distinction between what was confirmed and what was not. In addition of the oral authenticity, witness matching was to a certain extent, evidence of reliability.
There were no solid manuscripts that contributed to the production of the Quran, but as I said, the Quran is a unique form of literature with unorthodox, advanced authentication practices that were not seen in the early few centuries. Quran is unique in that it is the only source of its own and required majority voting of a group for authentication purposes justifying its written distribution unlike most religious material that were written and confirmed only by a few., thus compiling at a later time made more sense was made even more urgent when war killed most of the Quran reciters.