You are having a different debate because what you're talking about is not even tangentially related to the case. All I see here is a lot of flailing at imaginary "liberal" opponents not actually present in the thread, over vague ideas not actually relevant to the thread. Okay, great, you're mad at some libs you met at a dinner party. Sounds like a great topic for a blog post.
It would really have been helpful if you'd read what the charges are before debating them.
There was reasonable cause for suspicion that the law had been broken. After NARA discovered that a number of documents were missing, Trump's own people confirmed that they had boxes of documents that should've been turned over. This ultimately led to the discovery that not only had highly classified documents been mishandled, but Trump and his people had knowingly and actively attempted—on multiple occasions—to illegally hold on to those documents, even after it had become clear that they should've been turned over.
Notwithstanding the issue of criminality, getting those classified documents back was crucial to assessing potential risk to US security interests—including the identity and safety of HUMINT assets—and mitigating any risks that might arise from their compromise. That's without even considering the risk of US allies becoming more reluctant to share intel with the US.
The steps the DOJ has taken to investigate Trump—including subpoenas and warrants—have been approved by judges and grand juries, who have found reasonable cause to suspect specific criminal activity. When you say "the first line of defense will be there was no reasonable cause for a suspicion of the law having been broken" it just tells me you haven't read the first thing about the case you're discussing.
Trump is
literally on tape saying he can't declassify the documents in question because he's no longer president. That's his "doctrine".