And what if Comey didn't send the letter and due to a combination of FBI leaks and other factors Trump STILL won?
Comey did what he did because he had to cover for the possibility of Trump winning.
I don't see why things don't play out similarly. FBI continues investigation into Hillary's emails, continues to find nothing, eventually moves on.
The implication in thinking that things would have played out differently had Comey not sent the letter is that there's some sort of cover-up now, which there isn't. We all now know that the email "scandal" was bullshit. That doesn't change depending on who wins the presidency.
The conclusion that I reach is the exact opposite of yours. I think Comey did what he did because he expected Hillary to win regardless. Hell, almost everyone did.