Maul used your desire to do good to deceive you, and in doing so he has altered the course of many things. He knows your fears, your heart, and he manipulated the truth, which has led you here, where you should never have been.
What Obi-Wan said to Ezra was running through his head as he rode on his dewback.
For the last fifteen years he had lived on the desert planet known as Tatooine when he was assigned to watch Luke by Yoda.
He was sensing through the force that Luke would soon be needed to defeat Darth Vader and The Emperor.
However, he was afraid, fearing that Luke would become like his father, that their plans for the return of The Jedi Order would fail.
Encountering Ezra was not part of the plan, and almost risked everything from this event. Yoda has contacted from the force about the events of Malachor not going what they had hoped. Ahsoka's Force signature seemed to have disappeared following what transpired. Ezra and Kanan still lived. And that, was a problem, should they be around by the time Luke was ready, they would influence the boy with similar lessons that his father had learned.
They were not true Jedi, they gave into their emotions; their passions, a Jedi needed to be humbled, not be tempted by things that would lead to the dark side.
He could've left Ezra to his fate, but he sensed Ezra would be needed for something, The Force dictated that.
Maul's fate was sealed when he came to learn what Obi-Wan was protecting, he had to do what he must to preserve the Order's future.
I will do what I must, Obi-Wan. His master Qui-Gon had once said to him, now Kenobi must do what is necessary for the Order to survive these dark times.
What Maul had done to Ezra, it gave him an idea, for years, he had been trying to figure out how to approach Luke when the subject would come relating to his father. But Maul's actions today had given him what he had been looking for.
He would tell the truth, from a certain point of view. He would tell Luke about his father, but keep Vader as a separate entity. It would give Luke the necessity to be tuned to the light but not go out on a desperate attempt to 'redeem' his father, as much Obi-Wan wanted to believe turning from the Dark Side was possible, he knew it wasn't, as Yoda taught him. Once down the dark path, forever will it dominate your destiny.
He couldn't help but slightly thank Maul for this, he had given him the needs to make sure Luke put an end to Vader, and The Empire.
But now, he was pondering how to tell him when the day came he was needed. Obi-Wan stroked his beard as he watch young Luke run towards his aunt and uncle from afar.