What amazes me about Gundam is that it came out in 1979, just 3 years after O'Neill wrote The High Frontier but it completely adopted the aesthetic of that book.

Wars between space colonists and the Earth were a theme in Heinlein's 1966 The Moon is a Harsh Mistress and Haldeman's 1981 Worlds which came out just after Gundam. In that time-frame though there had just been the big success of the 1977 Star Wars and the re-release of Space Battleship Yamato and everybody was trying to rush out science fiction movies and TV.

Looking back though, the giant robots seem more plausible than the O'Neill style space colonies with huge airspaces. On the moon you can make as much aluminum, glass, dirt shielding, and oxygen as you want. What it lacks is inert gases such as nitrogen, helium, argon or materials to make SF6. If you try to breathe pure O2 you will burn out, not fade away

https://en.wikipedia.org/wiki/Apollo_1