Adrian couldn't possibly be unaware of how much vitality Apple had regained after Jobs made his return. It was one of the reasons he initially forged a good relationship with Jobs, with Pixar being the second.
But he was unclear about how Jobs could have made his way back to Apple or why he directed Apple to adjust its course. Perhaps the success of Pixar had increased his leverage and influenced him, but perhaps not—who knows?
Of course, just like that famous saying from Hollywood: no one is indispensable, not even Jobs was 100% irreplaceable. If Adrian were to take the CEO position at Apple, as long as designers like Jonathan Ive remained, he might not match Jobs, but he could at least achieve 80% of what Jobs did. Okay, perhaps that example wasn't quite right. Without Jobs, Apple might have faltered and declined, or they might have found a better CEO and achieved even more brilliant successes. The future draws people in with its uncertainty.