Yeah, I think the existence of the OT is pretty much the most important reason for all of this, including the incredibly stupid decision by Kenobi and Yoda to split up at the end of Ep3.
"Oh gee, two of us there are, and one of him. Incredibly powerful Sith Lord he is. Now that we know his new apprentice is away and interfere he cannot, we should split up and only one of us should fight him."
"Wait, master Yoda, don't you mean we should gang up on him and then once he's mincemeat hunt down his apprentice at our leisure?"
"Up, shut! I here the Jedi master am. Far lousier than yours my grammar is, which wisdom mine shows. Now as you are told go do, and perfectly fine this all will turn out."