Hey now!
Actually, I believe there's some merit to your theory...
Man evolved bipedalism to make fire and free their hands for shadow puppets.
Actually, I believe that bipedalism helped the hominids to carry fire. Making it came much later, I believe.
Fire occurs naturally. There are parts of Africa that burn every year. There are many reasons why an intelligent creature would be attracted to fire: it's interesting to look at, it gives light and heat, it scares away predators, it kills and cooks animals that lie there to be consumed.
I imagine that our ancestors made a habit out of looking for fire and staying near it. After a while, the fire dies out, and they have to move on. But wait a minute: fires can be fed and kept alive. I'll bet a chimp can learn to do that. Furthermore, it can be carried around from place to place.
Ah, but now look: the ape with the torch has gained a very serious, immediate survival advantage. Sabertooths (no offense) are suddenly no problem. Walking and seeing at night, no problem. Impressing the ladies, well, naturally.
This, I believe, solves one of the great problems of the evolution of bipedalism: a half-bipedal creature doesn't make much sense. The survival advantage conferred by partial bipedalism has to be immediate and huge, to get "over the hump".
Tool use is one obvious thing that can do this, but first of all, hominids were walking several million years before their brains expanded, second of all, there's not much need to carry tools that can be obtained whenever needed (sticks and stones are everywhere), and third, use of the simplest stone tools (unfashioned rocks used as hammers) doesn't appear in the fossil record until well after bipedalism. (Recent discoveries put the gap at longer than the two million years in my sonnet, which I wrote two summers ago.)
So, I really think fire is it.