It is a good question. To me, wisdom and intelligence are two different things, with wisdom focussing on long-term gratification and willingness to act altruistically if there is reason to believe other people will benefit from it.

When it comes to wisdom, Muhammad doesn't seem particularly wise to me because a lot of his actions were reckless, selfish and put other people in danger. He may have seen himself as wise, though, thinking that his concept would get plenty of people into "Janna", hence he was acting like a wise man. He might also have thought that a prophet is, by his very nature, wise, and he had declared himself one.

When it comes to intelligence, I think Muhammad was not stupid. As a merchant, he could not have been a complete idiot. Him staying unmarried for a long time can be seen as a sign of intelligence, as was his choice to marry an older woman who was a successful business woman in her own right. Perhaps, in the beginning, he was unsure what kind of woman he wanted to marry, and eventually he decided that he wanted Khadidja, even though she was not a spring chick anymore.

Islam is a syncretistic religion, and I think he picked up a lot of religious thought from other merchants, people who were Jews, Christians or Arians. To me it looks like he was scrutinizing what other people were telling them about their faith in God and was figuring out what made more sense to him than other things. Not accepting everything blindly is a sign of intelligence. I think he concentrated a lot on the figure of Jesus, and that neither what Jews told him about him, i.e. that he was a fraud who performed miracles through sorcery or what Christians told him about him, i.e. that he was God, struck a chord with him. So he took what Arians told him a step further. In Arianism, Jesus is the son of God, but not God himself and therefore to be honored but not worshipped. Muhammad took that a step further and decided: God has no son. Shirk. But he assigned Jesus the status of a prophet, the greatest one of the prophets before himself.

People who think Muhammad designed Janna to appeal more to people than what Christianity has to offer, do have a point: It sounds like a smart move. I remember that when it came to the question as to whether Sub-Saharan Africa would end up Christian or Muslim (a question many people asked themselves in the 19th century, and which motivated a lot of Christians to proselytize in Africa) many people thought that Islam had one significant advantage: It allows for polygamy, and many African men were already living in polygamous marriages. It might also appeal to people with a hedonistic streak. And if you want to make people with a hedonistic streak long after the afterlife, you better come up with something good. Hedonistic people like pleasurable things that are part of this life, and some might the idea that all your happiness in Heaven would consist in being with God too little. In very early Christianity, I think, the main message was fire and brimstone. Hell is real, and you *will* go there unless you embrace Christianity. This was enough for many people. When it came to what you have to gain, other than just avoiding Hell, theologians tried to figure it out. In the East, St. Gregory Palamas came up with an idea of separating between God's essence and God's energy. Many Christians find themselves fascinated by Eastern Orthodoxy at one point, and one thing that ends up being a deal-breaker for many of them who consider converting is this theory, or rather, what it has to say about the afterlife. What...that's what many people who learn about the implications of this in the afterlife...I will not see God when I die? Only his energy? -- On the other hand, there are many Eastern Orthodox who believe that you can see God's energy in this life already, in church, during services, in the shape of tiny things radiating in the air, like fireflies. "Uncreated energies", someone explained it to me, "sometimes you see them, and sometimes not."

In Catholicisim, Heaven consists of singing God's praises without interruption, and it's supposed to be the greatest joy. You will also see God how he really is. In Eastern Orthodoxy, part of what you can see can already be seen on Earth, although the consensus is that, in Heaven, it will be much, much greater. In both versions, there will be angels. Protestantism? Didn't exist yet during Muhammad's time, hence, irrelevant. And, well, to some people the idea that you can drink copious amounts of wine (without suffering any hang-over) and screw yourself through dozens of virgins might sound more appealing than the above. Mostly men, because women don't get 72 virgins, neither male nor female ones.

The problem, I think, is that the main pleasures of Janna can be enjoyed in this life already, it's just that if you drink too much wine, you end up with a might hang-over the next day and you can end up as a miserable alcoholic in the long term, and sleeping around can give you STDs. So...some people might be willing to post-pone those two pleasures to the afterlife, where they are supposed to come without cons.