When you get to the bottom line, the fact is that former Presidents are
not just like anyone else. A President is entrusted, by definition, with decisions that shape the future of the country, and they don't stop mattering when they leave office.
One example many people people forget, is how President Clinton asked former President Nixon for advice on Foreign Policy. And most recently, President Biden depended on former President Obama for advice on the Economy. You should understand that the current President in both cases shared confidential, even classified information with the former President in order for the former President to be able to advise in context. For as long as our nation has been a nation, former Presidents have been asked for advice and counsel, and have had access to restricted information to do so.
Also, consider if a former President decides to write his memoirs and wants to organize his thoughts on a sensitive topic, he will write down things he recalls, some of which is still going to be too sensitive to be released to the public. That is, former Presidents will have information in their minds which would be classified information by definition, and writing their memoirs could lead to first drafts which would essentially be classified information.
All of this applies to why former Presidents were never accused of crimes just for having classified material in their offices, especially when those offices were secured and guarded. At least, until the Biden Administration saw opportunity in going after former President Trump.
The glaring hypocrisy of the actions by the Archives under Biden is even more appalling when we consider that Biden had classified material for
decades in his house, material which as Senator and/or Vice-President he never had authority to move or keep in his personal residence, and let's not forget that multiple
boxes of those documents were on the floor of an unlocked, unguarded garage.
That which does not kill me, will try again and get nastier