Also there's a mechanism for taking into account charges like the campaign finance violations during his sentencing. (Which I'm not sure how I feel about)

And in general his sentencing was about whether they were going to put him away for a defacto life sentence or not. And I'm not sure that more charges for the same crime spree would affect that.

Also because the Bahamian government objected. The campaign finance charges were not part of the initial extradition request for SBF, so it was a sovereignty issue. The US prosecutors didn't press the matter, because they had him nailed for so many other charges, just as you say.

Salame was not extradited, so in his case, the US prosecutors could proceed with the campaign finance charges. That process ended with a guilty plea rather than a trial.

People will speculate about a conspiracy to keep the campaign stuff away from trial, but it all seems pretty routine to me.

"You follow drugs, you get drug addicts and drug dealers. But you start to follow the money, and you don't know where it's gonna take you"