Here are a few points to keep in mind.

The immunity of former Presidents is a long-held precedent and tradition in the US Constitutional system since the start.

It was seen as critical, because NOT having that immunity would make it extremely difficult for presidents to act confidently and decisively in office, if there was real potential that when their political opponents 'got in', that they would then be targeted and attacked for their actions in office. Elected Presidents have to be able to act with full confidence in their actions.

But here is the problem: The office of POTUS became corrupted. Certainly with Bush Jnr and Obama, but very likely from LBJ onwards, certain POTUSes have done very bad things.

Lot's of people get all upset because DJT is being attacked by Jack Smith, but is this really hurting Trump, or helping him? How many middle of the road people in the US do you think are having their eyes opened because of the way that Smith and all the other lawfares are being conducted? As DJT says, his poll numbers just keep going up and getting a boost from all of this. And that is THEIR fake polls, even.

Does the principle of presidential immunity need to be revisted? Should a president be immune from ALL actions taken in office? Can a president commit murder and be immune after leaving office?

Very possibly, the Smith case may actually be a necessary part of refining the principle of presidential immunity. It may be that the immunity needs to be refined and narrowed, for example, not to extend to ALL actions taken in office, but only to OFFICIAL actions taken in office. Aka actions and decision that are legitimately part of the presidential role, but not those that are NOT part of the presidential role.

Trump is innocent of any wrongdoing. We know he had an obligation by oath to take even the possibility of election fraud seriously. Nothing he did is outside of his official responsibility as POTUS.

But if at some point, Obama and Bush Jnr, for example, are to be held to account, then the definition of presidential immunity might very well need to be narrowed or more defined.

SCOTUS may very possibly deliver a judgment here that refines the definition and both exonerates Trump while also exposing previous presidents to liability for treasonous or other actions.

Either way, its not just a cut and dried issue, as far as I can see.