I think Obi-wan didn't do anything "wrong".
But neither did he anything right.
He wasn't able to stay near Qui-Gon in the EP1 final duel. That was why, Qui-Gon got himself leathally injured and got a chance to state his last-wish. Obi wan was obligated to train anakin, because he respected his former master so much.
So he trained anakin for Qui-gon. Not because he thought that he was up to the task himself.
He was unable to train anakin efficently enough, as he admits in ROTJ.
Then he was unable to destroy anakin once and for all when he got a chance for that.
Like I said, it was not his fault actually. He was just a victim of the circumstances...
But how could Yoda know that?