1. There's a procedure for declassifying documents. Trump did not notify the various branches charged with making sure that classified information doesn't fall into foreign hands, or those responsible for Freedom of Information Act requests. Like it or not, the US has a bureaucracy responsible for making the government run. The President is an important piece of it, but he doesn't have unlimited power to do whatever he wants. His powers are limited by the US Constitution, and nuclear weapons information in particular is controlled by Congress and law, not by the President.
2. Even if Trump *did* declassify them, he's basically admitting to keeping documents with top-secret information and reserving them for personal use. The details are still speculation because he didn't actually follow the process of declassification and has declined to share the details from the search warrant, but in context, the information could very well include nuclear secrets, sensitive information obtained from foreign allies, and the disposition of US forces. If you're concerned about protecting the United States, its troops, or its alliances, you should be very concerned. Actually declassifying such things wouldn't give Trump legal possession of the documents in question, and doesn't help to keep the US safe. Nor would it be a defense against the subpoena from the National Archives which Trump received, but which he apparently didn't comply with.
3. If these documents were related to the "Russia hoax", as Trump has implied in some cases, then it would have been in his interest to tell people the actual information - instead of spreading unsubstantiated rumors, as he has insisted on doing to date. If the FBI was "planting evidence", as Trump's supporters have claimed, then security cameras at Mar-a-Lago should support that. However, Trump's attorneys signed receipts for the documents removed from the site, and those receipts (and the warrant justifying their seizure) are now public.
4. If you claim to be a supporter of law enforcement, or like slogans like "Blue Lives Matter", you should be predisposed, in uncertain cases, to side with the FBI and the rule of law. Trump and his supporters plainly aren't. That alone doesn't mean they're guilty, but it does suggest they're hypocrites and that the GOP's prior support of veterans and police was mere political convenience.
5. Trump claimed at one point that if the government wanted the records back, they could have just asked - which they did. Those documents should have been handed over under law in January 2021. The National Archives obtained a court order for them in January 2022 - which was actively opposed by Trump and via multiple subpoenas in the months prior. Trump also has a documented habit of destroying documents that are of concern to law enforcement and national security, in violation of the Presidential Records Act.
6. Comparisons to Hillary Clinton are generally missing some important points: Clinton testified under oath on multiple occasions - which Trump has refused to do. Most or all of the missing emails were recovered by collecting records from those who regularly exchanged email with her. Only a small minority of the emails were found to contain classified information. After investigation, Clinton was found to have been sloppy in her handling of classified information, but there was no evidence of malice. Trump, by contrast, has actively opposed the release of information in many cases and ran on the idea that he would better handle classified information: He therefore has a harder time claiming he was ignorant of how to properly handle classified information, or that he would have cooperated had he been given the chance.
7. Similarly, the Steele Dossier was a minor footnote - and recognized to come from a biased source - in the initial investigations of Trump aides’ ties to foreign intelligence agencies. The Mueller report found extensive evidence of Russian agents interfering with the 2016 Presidential election, links between the Trump campaign and the Russian government, and Trump’s obstructions of these investigations. Those who link the FBI confiscating documents from Mar-A-Lago, and the January 6th Committee to the Mueller report are providing evidence of a long-term pattern of obstruction and suspicious activities by Trump. If this is all part of a single “witch hunt”, as Trump has claimed, it has found a lot of witches.