Lol, you thing that photoshopping technology did not exist in the 60s and 70s. You are more gullible that I thought.
Photo editing techniques did exist in the 60s and 70s, but they were
physical techniques which involved changing the actual photo. With technology like that you can't just
"create a fake image".
In regards to
"photoshopping technology", this was what a computer in the 1960s looked like:

At this point in history, in order to run a computer, you'd have to physically change out wires, or move tubes. Almost no computers from this era even had something reminiscent of a screen. Likewise, computers in the 1970s did have screens, but they were all comprised of low-resolution graphics and terminal screens. No
"photoshopping" techniques would have been possible to create a photo like the Blue Marble.