Smarts helps a lot, but one of the most critical attributes in football at that position, and really in anything where it's going to be tough and you're starting out pretty green, is just patience and humility.
A lot of smart, talented QB's, and yet barely any actually made a real impact. Why? A lot of it is coming from being a hotshot in college and thinking they're better than they are, or that they should be better, and that because they're this proclaimed high draft pick, they need to try and do as much as possible. Ego and impatience.
One of Dak's greatest attributes, and it showed in his background, especially after losing his mother, was humility. You have to understand that the NFL is a different level, and you know nothing. What you think you know, you don't. Once you understand the humility, then you have to have the patience. Rome wasn't built in a day. You're not going to turn into Tom Brady in one week. You're not going to learn an NFL playbook in a month. It's not happening. That's also humility understanding your limits.
What Dak did was do exactly what the coaches told him to do, checked his ego at the door, and worked his butt off. He didn't try to do too much at once, because he knew, no matter what his success was in college, no one is good enough to do that in the NFL, not even him.
And the "calm". There are few guys I've seen (energy and now tech) that have that ability to never have their blood pressure rise, even in the craziest moments. They mentioned in the earlier part of the season. That's one of the rarest traits you'll ever find. I'm sure some guys in the military have had guys above them in the ranks that had this trait, it's otherworldly. Combine that with the humility and the patience, and obvious rare physical ability compared to normal humans, and you have Dak.
I honestly think, even if Dak isn't a real "3.5-4.0" student, he'd probably succeed in anything he did in life with the right mentor.