I think at least half of it is a Nausicaa reference, the movie was a huge hit and must have had a huger influence on things. Crystalis for instance. Think of it how certain games wouldn't exist, or at least not be the same way, if it wasn't for Mad Max.
And it's not exactly something new either. Lots of older works we classify as fantasy actually take place in our world but either insanely far into the future/past. It's just a cool concept with fucks with our idea of linearly progressing era.