We have had a lot of different kinds of President in my lifetime. If someone can manage to get elected, anything that they lack can be supplied by helpers. Yeah, it is reassuring when a candidate can answer a lot of cold questions, because it demonstrates that they've thought things through and have a foundational understanding. Someone like that can be counted on to be consistent. But it isn't actually necessary for them to know all the answers. I haven't been watching interviews. I saw Kamala Harris dodge some questions in the debate (and a lot of times in the weeks after Biden's debate). I guess I don't understand how she was childish. She was evasive and that is how someone is when they mean to evade something. When I have seen her evasive, it was when she was asked a question whose possible answers are both problematic. She is in a delicate position, wanting as much of Biden shine as she can get and as little of the stink. The other side is trying to reverse that on her and the path between the gutters is narrow. There is no politically advantageous answer to "You've been in there for 3.5 years, why haven't you already implemented your plan." The answer is that she hasn't been in charge, but she cannot have a recording of that in her voice. I haven't seen her dodging questions because she didn't know the answer. Maybe someone could provide me a clip.
Ultimately, I'm not concerned with whether either of them knows the answer to a cold question. I do not want a President that makes snap decisions and I also don't want one that thinks they know everything. I wish candidates would say they didn't know when they didn't know. The President always has enough time to ask for some advice, even with an ICBM in the sky. And there's pretty much no one who won't answer when POTUS asks for a phone a friend.
The absolutely essential skill that cannot be supplemented is the ability to assess their own abilities. If you don't know you need help, you won't get it. Something that has been very clearly and very openly demonstrated for more than a decade is that Donald Trump is a total failure at assessing his own abilities. With all of his terrible shortcomings, he could be a much better President if he would read his teleprompt, vet his public statements, and find and heed good policy advisors. But he won't. You know he won't. I believe Kamala Harris will get advice and make a good first draft on building her team and I believe she will also listen to criticism and adapt. Not because of what I've seen her do, but because people who are elected President do this. It's the normal thing. They want to do a good job, whether because of patriotism or because history has its eyes on them. Donald Trump not doing it is an outlier.
That clip above is a preeminent demonstration of Trump's problem and he won't see it. He is criticizing Harris' ability to answer a cold question, because he believes he does it well and he doesn't. His failure to see that is why he is a failure as a leader. News media said Harris had intense preparation for the debate and I think there is probably an indication in there that some of the skills to win a debate are struggles for her, but she practiced and prepared and she mopped the floor with him and none of THOSE skills themselves are the essential skill that she needs. The essential skill was that she did the intense preparation because she knew she needed it. The whole week leading up to the debate CNN was reporting that insiders said Harris would goad Trump's ego to knock him off balance. I'm sure his campaign reads CNN. I'm sure they mentioned it to him. But it still worked. Because Trump has no story arc. He will not improve himself. He will not listen to good advice. His shortcomings cannot be bridged.