We should be open to the idea that Russia indeed might want Bernie. Russia wants the US to be unstable. The US needs what Bernie has to offer but Bernie is disruptive and him running against Trump is certainly good for popcorn sales in Russia.
But ther are other reasons Russia may want Bernie. On the international stage Bernie may be much more pragmatic. People applauded Trump for saying that he would not bring the US into useless wars but they misunderstood what Trump meant until Trump was proud to say he dropped the biggest non-nuclear bomb ever. Sanders would likely make Russia easier to govern. As Sanders may focus more resources on domestic US he would free Russia (with a much smaller economy) to do the same. Sanders is less likely to destabilize the world in ways that disturb not only Russia but many countries. This does not mean Russia has a friendly outlook on the world but they woudl prefer a Sanders to an old fashioned Democrat cold warrior.
The Russians probably do not fully understand Sanders: if he won he might make the US much stronger, even if they are less menacing. The US is rotting from within. Their economy is a sham of credit and debt due to inequality. Sanders might offer the last best hope of the US stepping back from the brink. On the other hand, the Russians don't want the US stronger than them but they probably are reasonably afraid of what the US would look like in freefall. Far too much of the well being of the globe is threatened by the US either in ascendency or in collapse. The Russians may understand that the US may be in decline but a sudden collapse is bad for the world compared to a slow decline. Sanders dramatically could reduce the chance of a sudden collapse by shoring up the weakest element of the US: the welfare of the people.
I would guess that most people in the world could rationally determine that Sanders is the best bet not just to beat Trump, who is clearly dangerous, but also to avoid the standard US democratic cold warrior. Trump may be Russia's first choice (or not) but Sanders is a good pick for them for the same reasons that he is a good pick for every other country in the world.
I still have not understood any reason why the US would feel that it would gain anything by interfering in this election. The US is either screwed which is okay or will pick a candidate (Sanders) who would be less harmful to the world. Seems that in a Trump-Sanders matchup the Russians win either way: either the US will harm itself and be less harmful to others or it will help iteself and be less harmful to others.
I believe the Russians are not now a positive force on the world stage either but that does not mean they would not gain out of the US being better. Now that said a Bernie Presidency could create all kinds of positive shifts in the world and that could even include much better communications between Russia and the rest of the world.
On that point -- Putin is also a product of context. Had, Europe and the US welcomed Russia in the 1990s in a positive way, Putin likely would have had a different world view and liekly would not even be the leader. His politics is informed very much by the betrayal of Russia by the US and Europe that took place in the 90s -- and the hostile posture then taken against Russia. Any understanding, even the most basic, of Russian history would have led to the ability to predict this perfectly -- and some did at the time.