George Lucas seemed to think that any compromise messed with his vision. He seemed to think that only he was capable of knowing what was best for his franchise. He blatantly disregarded the work other writers and creators had built around his own works, and instead of acknowledging them with gratitude he proceeded to ignore them and do his own thing.
I can't really fault Lucas for this. The Expanded Universe is pretty f***ing huge, and to go through and figure out what should be canon and all that junk. It's easier for him to just say the stories he's told are canon, because the EU spends a decent amount of time contradicting itself on a regular basis.
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TheRock ~ Slow dramatic zoom-pan. Doesn't phase the hooded man.