Idunno if this tidbit has been offered up in this thread, or whether or not it’s generally known, but … more important than the Presidential/Federal Records Act(s), in this case, may be the following portions of 44 U.S. Code § 3106 - Unlawful removal, destruction of records:
(a)Federal Agency Notification
The head of each Federal agency shall notify the Archivist of any actual, impending, or threatened unlawful removal, defacing, alteration, corruption, deletion, erasure, or other destruction of records in the custody of the agency, and with the assistance of the Archivist shall initiate action through the Attorney General for the recovery of records the head of the Federal agency knows or has reason to believe have been unlawfully removed from that agency, or from another Federal agency whose records have been transferred to the legal custody of that Federal agency.
(b)Archivist Notification
In any case in which the head of a Federal agency does not initiate an action for such recovery or other redress within a reasonable period of time after being notified of any such unlawful action described in subsection (a), or is participating in, or believed to be participating in any such unlawful action, the Archivist shall request the Attorney General to initiate such an action, and shall notify the Congress when such a request has been made.
TL;DR: the people who sicced Justice on Trump were legally obligated to do so under these US Code sections.
That’s the difference between “shall” and “may.”
Which, arguably, makes the case even stronger than the basic, “It’s his own fault. If he had given them back …” He actually created a situation that, legally, took the choice away from the Federal Agency heads AND NARA.