Yeah, I heard. Aliens, nuclear explosions??? What a rip-off. Indy's always been about the occult and booby traps, not aliens and nuclear explosions.
Oh well, Lucas was probably looking at the "not quite what he thought" returns from the Star Wars prequels, saw that it wasn't enough, and knew he could put out some crap movie with "Indiana Jones" on it and cover whatever he thought he was supposed to make. Or something.