it was b/c anakin wasn't thinking and being patient like obi-wan taught him, but if you have played Revenge of the Sith video game after beating the game you get to play 1 more level on mustafar but this time as anakin facing obi-wan and you win but doing like in the movie jumping towards him BUT instead of jumping over him and him cutting your legs off, YOU JUMP OVER HIM AND BRING YOUR LEGS TO YOUR CHEST AND LAND BEHIND HIM AND STAB YOUR SABER INTO HIS BACK THREW HIS CHEST KILLING OBI-WAN thne you kill the emperor with your new red lightsaber when the emperor says "good... now no one can stop us this galaxy will be ours



Anakin: *stabs Emperor in the chest letting his saber sizzle in his chest for awhile before pulling it out and then says "NO! THE GALAXY BELONGS TO ME!" as clone troopers stare at him.