Perhaps it was Lucas' desire to build his own studio and be independant that caused him to start cheapening the series around Jedi (which I still believe was very good despite being very straightforward), but that excuse doesn't transate to the PT where his dreams have already been achieved. Plus, he was still making a lot of money going the more artistic route (ESB), just not as much. I believe he's just greedy and always wants the most money in exchange for the least effort.