The fact that Lucas decided at the last minute to kill off Obi-Wan Kenobi when he was making Star Wars gives you a window into the way he writes.

Kenobi was supposed to be the one who trains Luke to be a Jedi in the Star Wars sequels. But all Lucas cares about is the movie he's currently making. In every interview he's ever given on the subject, Lucas consistently gives the same two reasons for the decision to kill Obi Wan off in Star Wars:

1. Obi Wan doesn't have anything terribly significant to do except stand around for the last 20-30 minutes of the first movie

2. Killing him is more dramatic or interesting than him just standing around

So even though Obi Wan served a very necessary function in the Star Wars sequels, Lucas killed him off just to make things more interesting in the movie he was currently making at the time. Now we get to have Kenobi speak to Luke as a disembodied spirit during the final battle, instead of standing around nervously with everyone else down on the rebel base. Of course that created an issue he would now need to solve when it came time to write the sequel, but he figured that's a problem for later, and he'd just cross that bridge when he came to it.

Mind you, this is the story behind how Yoda came into existence, to solve the dilemma Lucas made for himself by killing off Kenobi. And of course everyone loves Yoda. So I'm not necessarily complaining. But this is an illustration of the subject of this thread, which is that Lucas has a very "make it up as I go" style of writing. There have been good results (Yoda). But the results aren't always good (Padme dies in childbirth??? No thanks).