"Whatever the outcome, it's not going to move the needle much on public perception."

Sure it will.

I mean to your point there is a solid 30% or so of Americans who won't care if he is found guilty they will still support him and there is 30% of Americans who will still think he is guilty if he is found innocent, but there is a portion in the middle where it will matter.

The 2020 election had a huge turnout because there was a decent size portion of Americans who are not really all that political and are not hard core members of any tribe, but they turned out because they realized just how bad Donald Trump was for America and how much of a threat he was to democracy (and this election took place before all of his shenanigans surrounding January 6th came out).

The result of this trial will matter.

Besides, public perception isn't the only purpose here. Rule of law matters as well.