Why does The Ancient One think differently about Doctor Strange in Endgame than the film Doctor Strange?

Question

In Doctor Strange, we see that, when Strange is seeking healing, he is rejected by The Ancient One, and if Mordo had not convinced her to change her mind Strange would probably never have been trained.

So, considering this evidence, The Ancient One seemed to have little to no faith that he was worth training.

However, in Avengers: Endgame, while Banner is attempting to retrieve the Time Stone from the past, The Ancient One mentions that:

Strange is meant to be the best of us.

She also mentioned that Strange was still working as a surgeon and had not been trained yet, therefore this happened before she had rejected Strange in the Doctor Strange film.

Based on the scene in Endgame she clearly knew the vital role Strange would play in the future. However, the scene in Doctor Strange is contradictory to that, showing that she did not believe training him would positively impact the future.

How exactly do these seemingly contradictory scenes fit together?

Answer 1

It appears to be part of Strange’s training and his journey to become who he is supposed to for The Ancient One to treat him as she does in Doctor Strange. Like with what Strange does in Avengers: Infinity War she has looked into his possible futures.

The Ancient One: Do you wonder what I see in your future?

Doctor Strange: No. Yes.

The Ancient One: I never saw your future, only its possibilities. You have such a capacity for goodness. You always excelled, but not because you crave success, but because of your fear of failure.

_{Doctor Strange}

The conversation continues and shows part of what this part of her teachings were all about for Strange. She is trying to teach him some vital lessons with selfishness just as she is trying to teach Mordo to be more flexible.

Doctor Strange: It’s what made me a great doctor.

The Ancient One: It’s precisely what kept you from greatness. Arrogance and fear still keep you from learning the simplest and most significant lesson of all.

Doctor Strange: Which is?

The Ancient One: It’s not about you. When you first came to me, you asked me how I was able to heal Jonathan Pangborn. I didn’t. He channels dimensional energy directly into his own body.

Doctor Strange: He uses magic to walk.

The Ancient One: Constantly. He had a choice: to return to to his own life, or to serve something greater than himself.

Doctor Strange: So, I could have my hands back again? My old life?

The Ancient One: You could. And the world would be all the lesser for it. I’ve hated drawing power from the Dark Dimension, but as you well know, sometimes one must break the rules in order to serve the greater good.

Doctor Strange: Mordo won’t see it that way.

The Ancient One: Mordo’s soul is rigid and unmovable, forged by the fires of his youth. He needs your flexibility, just as you need his strength. Only together do you stand a chance of stopping Dormammu.

_{Doctor Strange}

Remember how in Avengers: Infinity War and Avengers: Endgame there was only one winning possibility and Strange couldn’t tell anyone if they were under that play still else it wouldn’t happen. A similar thing is happening here. For Strange to turn into the best of us he must walk a specific path that has The Ancient One giving him a hard time. Of course here that specific path also forms an extra purpose because it helps Strange let go of his own selfishness.

As part of this path she wanted Mordo to battle for Strange, which he does, as Mordo is a vital mentor and it also helps him on his own journey. The Ancient One’s final words in the below quote are quite telling as to what she is actually trying to do here; she is guiding the both of them to become who they need to be.

The Ancient One: Thank you, Masters. You think I’m wrong to cast him out?

Mordo: 5 hours later, he’s still on your doorstep. There’s a strength to him.

The Ancient One: Stubbornness, arrogance, ambition…I’ve seen it all before.

Mordo: He reminds you of Kaecilius?

The Ancient One: I can not lead another gifted student to power, only to lose him to the darkness.

Mordo: You didn’t lose me. I wanted the power to defeat my enemies. You gave me the power to defeat my demons. And to live within the natural law.

The Ancient One: We never lose our demons, Mordo. We only learn to live above them.

Mordo: Kaecilius still has the stolen pages. If he deciphers them, he could bring ruin upon us all. There may be dark days ahead. Perhaps Kamar-Taj could use a man like Strange.

_{Doctor Strange}

Answer 2

She doesn't think he's worthless. She just acts that way in Doctor Strange because that is pretty much standard for the "Eastern martial arts teacher" trope.

In the western teacher trope, the teacher searches out and courts brilliant but reluctant students, and bends over backwards to extract their greatness, in a game of Pygmalion: like Robin Williams in Goodwill Hunting or Dead Poet's Society. The student "acts up" to reject/test the teacher, and the teacher ignores this insult and persists, ever trying to convince the student of their worth.

In the eastern trope, it's the other way 'round, like in The Karate Kid or William Dale Jennings' The Ronin. The teacher is reluctant and annoyed. The student bends over backwards to seek their expertise, while the teacher "acts up" to reject/test the student. The student ignores this and persists, ever trying to prove their worth to the teacher. The teacher rejecting the student out-of-hand and the student camping their doorstep for days is typical.

Mind you, the Ancient One knows Strange won't easily give up, so she knows how far to test him. To be more precise, she knows exactly what will both engage Strange and lead him to the greatness she foresees. If Strange needed the Robin Williams treatment she'd have probably given it to him; but just like Strange sees "1" outcome where we win, likewise the Ancient One sees "1" outcome where Strange becomes who he needs to be. So it's Strange as much as her who expects the eastern teacher treatment.

Answer 3

When Strange first came to the Temple, he was still the arrogant doctor, that valued his own reputation above human life.

Doctor Strange: [To Billy, on the phone.] Billy! What have you got for me?

Billy: I’ve got a 35-year-old Air Force colonel. Crushed his lower spine in some kind of experimental armor. Mid-thoracic vertebral fracture.

Doctor Strange: Well, I could help, but so can 50 other people. Find me something worth my time.

Billy: I have a 68-year-old female with an advanced brain stem glioma.

Doctor Strange: Yeah, you want me to screw up my perfect record? Definitely not.

Billy: How about a 22-year-old female with an electronic implant in her brain to control schizophrenia struck by lightning?

Doctor Strange: That does sound interesting. Could you send me the… [His phone screen lights up with the patient's documents] got it. Hey.

He was only following a lead, after he'd already spent everything he had trying to recover the damage to his hands, so that he might again be able to perform his miracles in the surgery, and when the Ancient One showed him the power of the Masters of the Mystic Arts, he saw that as power; a tool he could use for his own gain. This is what the Ancient One saw, and refused him.

This is where Mordo stepped in. He convinced the Ancient One to let him join the Temple, and learn, under his guidance and tutelage. Mordo was on one of the higher ranking Sorcerers in the Temple, and she trusted his judgement. She saw what he had come from, and what he had become; and trusted him to guide Strange down the same path.

Mordo: [to Strange] I once stood in your place. And I, too, was... disrespectful. So might I offer you some advice? Forget everything you think you know.

With the proper guidance, Strange lost the desire for power, and gained the desire for knowledge. His curiosity and desire for understanding became the driving force behind his actions.

And as DariM mentioned in their comment:

The Ancient One can see possibilities, but those possibilities are still dependent on the individual actions or choices of people.

Strange, alone, if given the opportunity would have not become who she saw him to be. With guidance from another Sorcerer, however (Mordo), she saw that Strange would become "The best of us".