This is going to drive him back to madness, Strange can tell that much already. Because he should know. He should know why he couldn't save Tyki and what prevented him from doing so in the first place. Strange takes another step backwards, looking utterly distressed for a moment.

"Something must have happened," Strange repeats, more to convince himself than to convince Tyki. "Or something must have stopped me."

And he looks over at Tyki with a frown. He doubted Tyki tell him. But it can't hurt to ask. "You still can be saved. I just need to know what stopped me to begin with." Don't ask him how he knows, he just knows. Enchantments can be broken. If someone twists your mind, it can be fixed. But that doesn't change the fact that Strange has no idea how he'd even start to go about saving Tyki! And that doesn't hide the note of desperation that's staring to creep into his voice.