that's speculation, of course, but it makes sense to me.
Rodan returned in 1964's GHIDRAH, THE THREE HEADED MONSTER. he didn't quite look the same, but still pretty good. this is Rodan in space, from MONSTER ZERO (1965). the suit looks good, though the neck is pretty long, which leads to some goofy looking shots. I am not sure what the thinking is behind this, but it mostly fits in the movie.