Why does that matter? The crime was ALREADY committed. Telling a speeder to pull over [to stop speeding] doesn’t mean that you no longer committed a crime. The subpoena just substantiates the fact that a crime was already committed.
Not in this case.
Remember, there are three statutes that were cited in the search warrant. The one with the easiest intent requirement to prove is 18 CFR 793, which provides (in relevant part):
(d) Whoever, lawfully having possession of [lengthy description of defense information] willfully retains the same and fails to deliver it on demand to the officer or employee of the United States entitled to receive it;
The crime isn’t that he retained the documents when he left office. The crime is failing to deliver it when a U.S. officer demands the documents back. If Trump can produce evidence that he directed his agents (employees or lawyers) to give back all the documents that the government was entitled to, that he knew a tranche of documents was returned to the government, and that he was not thereafter informed of what documents were retained, it will be difficult to meet this burden of proof. If he can raise reasonable doubt as to whether he knew that any defense documents were among the ones that weren’t given back, he can get out of this statute.
The other two statutes have looser requirements for the actions involved. He merely has to have had done some prohibited things with any government documents, and they don’t have to be defense documents. But they have tougher intent provisions. One of them you have to prove that his intent was to obstruct an investigation - which will be very hard, since he can easily show other motivations as alternatives for why he kept the documents (like boosting his ego).
The last is the generic “stealing documents from the government” statute, but the language is a little tricky.
Whoever, having the custody of any such record, proceeding, map, book, document, paper, or other thing, willfully and unlawfully conceals, removes, mutilates, obliterates, falsifies, or destroys the same, shall be fined under this title or imprisoned not more than three years, or both; and shall forfeit his office and be disqualified from holding any office under the United States.
You have to show that he unlawfully removed or concealed the documents. But if the documents were removed while he was still President, it’s hard to argue that the removal was unlawful - because at the time, he had the authority to direct that they be moved to Mar-a-Lago. He certainly retained the documents thereafter - but that’s not one of the things that statute prohibits. Did he “conceal” them unlawfully? Again, hard to say - because if he moved them to Mar-a-Lago while he was President, then he didn’t take any unlawful actions to conceal them - all his actions hiding them away were done while he was President. “Conceal” probably isn’t the same as “fail to disclose” - and virtually all the records were shown to the government agents when they came to review the documents at Mar-a-Lago, just not returned to the government. It might be hard to pin a “conceal” charge on him for those documents.
That just leaves the documents in the safe - and we don’t what those are. Those probably give him the worst exposure, since (unlike the basement) there’s a good chance that a jury would believe that Trump knew the contents of his own safe, and would have known that none of those documents were returned.