Trump knows it is not a crime to spin out crazy legal theories (like he has a right to the documents) or to lie like a rug, if not under oath, and does so with regularity because he is a sociopath. Someone ratted on him about culling the documents to decide which ones he would decide to secret.
It is certainly not a crime for Trump to spin out crazy legal theories.
However, what he said, and this is a direct quote, was "
I would do that."
He didn't say "I could do that." He said that he "would" do that, not the word "could." If he had said "could," that would be him saying, as a matter of legal theory, that he could do that, and so that would be just spinning a crazy legal theory, which by itself would be fine (legally) for him to do.
But he went beyond could and said that he actually
would do that, that this is actually something that he had the sort of intent and frame of mind that he would actually do, not just theoretically.
Granted, he did not say that he "dd" do it. If he had used the word "did," rather than "should," then it would have been an outright admission that he did it.
But still, saying "would" rather than merely "could" seems pretty significant, because it is an admission that it is the sort of thing he could do. In other words, he would say that it is not crazy to think that he would do that. That admission makes it a lot more plausible that he in fact
did do it.