If one cannot travel faster than the speed of light as maintained by Einstein, why does his famous equation about mass and energy talk about squaring the speed of light?

Because his formula describes the relationship between mass and energy, not speed? The speed of light squared is just a fundamental constant of nature, and that's how it's used in this formula. It is amazing that you can relate mass and energy in this way, the things that you are using the equation to describe don't even have to be moving at the speed of light!