Marquand was actually a very competent director. Lucas ended up being on set a lot because of Marquand’s inexperience with special effects. So George had to be there to make sure everything would mesh with ILM. But being on set, he clearly had opinions on what was going on with his movie, so he ended up basically being backseat director to Marquand in the process, which I’m sure Richard was just thrilled about.

So in short, I don’t think George planned on being on set so much, but it ended up that way anyways and I guess he just figured “while I’m here anyways…”