Ok, I'm just starting to read on the Lore of Fallout, but one thing I am curious about is the Cause of The Great War...

They say it's for lack of Fossil Fuels, but why would they fight over that, if they have the Tech. to produce all the things we have in Fallout, Energy, Plasma, etc. Am I missing something here?

It wasn't only fossil fuels, but all important energy producing elements were being hoarded and fought over. Imagine our world (irl) but with 3/4 of our energy producing elements (fossil fuels, plutonium, uranium, tritium, etc.) Cheap, clean, energy wasn't becoming perfected till about the same year as when the bombs dropped. Even the nuclear cars (like the Corvega) were still running on gas as well as fissionable material (Personal logs in Dead Money refer to "Chryslus gas hogs" )

With the world population still rising, and "known" energy sources drying up, the resource wars began.