There are a number of reasons this makes no sense, including Russia conspiring with a candidate who everyone (except for poly on this board) thought was not going to be the nominee, and if he was the nominee would get crushed by Hillary. Why the heck would Russia conspire with someone who nobody believed had a snowball's chance to win? If anything, they would have conspired with Hillary, especially given her "seedy ties to Russia."
Let's say you're judging a talent competition. You've got two contestants: one a classically trained pianist who's been playing for decades and the other a self-taught pianist who started playing a few weeks ago. Most people are assuming the trained pianist will win. You approach both of them and say "Hey,I can make sure there are some problems with the sound system during the other guy's performance, but you gotta give me half of your prize money." Assuming both want to win equally as badly, who is more likely to reciprocate? The frontrunner or the person who appears not to have a shot in hell?
Now let's say the trained pianist has said some pretty nasty things about you in the past and you two have a pretty bad relationship. Meanwhile, the underdog pianist has said a lot of flattering things about you. Which of the two contestants would you be more interested in helping: the one with whom you have a bad relationship or the one who has said nothing but kind things about you?
Now let's say you have a small business that hasn't been doing that well lately. If the winner of this contest decided to come by your store and mention it in their victory speech, that could really help you out. Who would be more likely to want to go the extra mile for you? The frontrunner who was probably going to win anyway and doesn't really care for you too much? Or the underdog who probably wouldn't have won without you.
I'm sure your answer is that both are just as likely to take you up on your offer and you probably have some new, bizarre definitions for "pianist", "contest" and "underdog" that prove it, but most people operating in reality would say that there's a clear difference between how receptive each party would be in each configuration because there's a clear difference in how much there is to gain for each party in each configuration. Whatever influence Russia had over the election wasn't a zero sum proposition.