Do you believe that Russia benefits equally from the election of either candidate this time around?
Also, https://en.wikipedia.org/wiki/List_of_Russian_assassinations
The distinction between Biden and Trump is that Trump is opposed to the machine that's been responsible for decades of disastrous foreign policy, while Biden is the face of that very same machine.
Putin is far from the only foreign leader who would prefer Trump. It's silly to attempt this framing.
But what if the decision is between a stability candidate and a pro-chaos candidate? I think then that Russia would take a side. And I doubt many would debate that one candidate is clearly more pro-chaos than the other.
It went far beyond a couple of artificial protests.
Russia did support Trump in 2016 (and beyond), Trump was quite happy about it.
If you were Russia in 2016, would you have preferred that the next US President be someone competent with significant foreign policy experience, or a Putin-idolizing fool with zero foreign policy experience?