Why not, "Allah" never messaged "Allah" was going to protect the texts of those religions that promise was only given to the "Quran". With the context "unlike before where the responsibility of maintaining the text was put upon humans, this time "Allah" takes that responsibility."
At that time, "Allah" allowed people to corrupt it. If people were restricted to sin, restricted to defile what is holy, restricted to corrupt. Than how can "Allah" have the evidence that those people who would like to use religion for their own desires and that people who allowed it are equally guilty because it worked out for them.
And its not a common con artist, its those with ambition and is educated in the matter enough that it can fool the people around them and/or play into their depravity.
And to what makes me sure the latest wasn't one. I read its life on the basis that information is true. The rank of prophet came to him when he was 40, and till that he lived his life with absolute trustworthiness. Old habits die hard.
all religions and this is only my opinion. start with something true, something confirmed, something which came with a prophet. But as time passes you get people who want to glorify certain people by raising them to godhood. rise certain people to a certain status of a saint to which can be prayed to. Decrease god to something of a mortal with immortality and superpowers in which they have to build an entire system around it to fool people that it works like that.
Edit: To clarify my last opinion, it the "Quran" it states that every tribe on earth has been send a prophet.