If you told me this was one player's attempt to make a single work of fiction out of a few year D&D campaign, I would completely believe you.
I'm not sure why it kind of works honestly. Perhaps it is just that it is so earnest and unabashedly straightforward in its definition of good vs evil? In the plot driving power of radiation and the mutations they engender? In the "hidden powers" of the human mind (very 1970s)? It is just so... unabashedly silly and yet genuine at the same time.