Fynn didn't get off if the feds dropped the charges, he was not found innocent by a jury so no double jeopardy applies and the feds can later indict him as part of a conspiracy, or even on the original charge. He's not out of the woods by a long shot. Trump won't pardon any potential witnesses against him because it would remove their 5th amendment rights and they would have nothing to lose testifying against him with a get out of jail free card. Why risk perjury for Donald when your home free? He has yet to pardon anybody who can be a potential witness against him and I'm sure he was warned about this too by lawyers, maybe commuting sentences, but no pardon.