This is a great question and I am sure that you will get many different responses. As you probably know, religion is one of those hot topics, which can cause a lot of emotions. In light of this, let me make a few observations.
First, you are correct, there are many religions around the world. Most of the world is religious. This is an important starting point, because in the West many educated people do not see this. Atheism is in the minority. Moreover, many intelligent people in the world believe in some divine being or beings.
Second, part of the reason why there are so many religions is rooted in culture. People from different places in the world have different convictions and beliefs. For example, if you live in the Middle East, you would realize that most people believe in one God. In India, most people have a polytheistic world view.
Third, human knowledge in many areas is limited. This is certainly the case when it comes to religion. The upshot of this is diversity of religions.