We are told diversity exists in the animal kingdom because of the process of evolution. Diversity exists in our solar system and the universe in general because of natural laws that govern our environment. Diversity happens because of organic progressions, happenstance, and a myriad of other factors which, as of yet, are difficult to be quantified.
All of this appears logical on the surface. But there is an underlying reason why planets are formed differently, animals evolve along a certain path, and why some suns are hotter than others.