I think that Mohammed authored it (he didn't 'write' it, obviously) with confederates, yes. I accept he was illiterate, and possibly even 'unlearned', but his achievements suggest he had both a mind of the first order and an indomitable will and sense of purpose so I don't see either as being insurmountable stumbling blocks. They had 'ghost writers' even in ancient times, if one or more was needed.
My reasons are partly that the Qur'an includes so much recycled material from earlier religions and beliefs, both from the Abrahamic traditions and otherwise, but mostly because it was so obviously written as a means of gaining political control and a general acceptance of particular social behaviours. It is part of Mohammed's genius both that those are generally beneficial social behaviours, and that most are relevant even up to the present day. I do not rule out considerable religious motivation, as an expression of his own beliefs, as well.
Before someone who shall remain nameless attacks me for presenting that as the 'truth', I am not, it is merely my opinion. I do not rule out the possibility that might change one day, at which point I would instantly become a muslim. I just don't see it happening; with one exception I find the suggested reasons to believe divine authorship unconvincing and in some cases, particularly the 'he couldn't possibly have known what science only discovered last year' routine, ridiculous. The exception, incidently, is a point most frequently made here by Woodrow that the Arabic itself simply could not have been written by a human being, or human beings, although others seem to disagree. I cannot fairly consider that without learning Qur'anic Arabic myself. I might just do that one day.
Well you might consider this as Political as well then: Allahu kalam "Al Hajj(22):40 Those who have been driven from their homes unjustly only because they said: Our Lord is Allah--For had it not been for Allah's repelling some men by means of others, cloisters and churches and oratories and mosques, wherein the name of Allah is oft mentioned, would assuredly have been pulled down. Verily Allah helpeth one who helpeth Him. Lo! Allah is Strong, Almighty.
Perhaps this is also Political to you:
Al Baqarah (2):109 Quite a number of the people of the Book wish they could turn you (people) back to infidelity after ye have believed from selfish envy after the truth hath become manifest unto them; but forgive and overlook till Allah accomplish His purpose; for Allah hath power over all things.
Al Imran (3):159 It is part of the Mercy of Allah that thou dost deal gently with them. Wert thou severe or harsh-hearted they would have broken away from about thee; so pass over (their faults) and ask for (Allah's) forgiveness for them; and consult them in affairs (of moment). Then when thou hast taken a decision put thy trust in Allah. For Allah loves those who put their trust (in Him).
Al Maidah (5):13 And because of their breaking their covenant, We have cursed them and made hard their hearts. They change words from their context and forget a part of that whereof they were admonished. Thou wilt not cease to discover treachery from all save a few of them. But bear with them and pardon them. Lo! Allah loveth the kindly.
Al Hijr (15):85 We created not the heavens the earth and all between them but for truth and just ends. And the Hour is surely coming (when this will be manifest). So overlook (any human faults) with gracious forgiveness.
Assalamu manit taba'al huda (May peace, development and safe from guile be upon who follow the guidance).