I mean, come on, a lot of us here know how web sites work. For a major country's spy agency, it would be trivially easy to automate account sign up and posting. Is it that hard to imagine? And when every dumb Joe on the planet is likely to believe the first thing they read that strategically appeals to their emotions? You do the math.
The problem is that you also need the gutted Voting Rights Act, rampant GOP gerrymandering, and the ridiculous favouring of Southern States by the Electoral College to get the win - and those have much more of an effect than a Russian finger on the scales.
Who stands to benefit or avoid harm from such a belief? Arguably the people responsible for the national circumstances that lead the population to vote for someone like Trump.
Growing wealth inequality? No, it's Russia
Questionable foreign wars? No, it's Russia
Massively deprived communities across the states? No, it's Russia
Off-shored working/middle class jobs? No, it's Russia
The Russia narrative is extremely attractive to those whose policies have been very unpopular with a large segment of society. Providing this can be kept up through the Trump presidency than the Democrat (and Republican to some extent) lines do not need to change. More of the same. It is not that people don't like our policies, they were just duped by Russia.
To believe that the effects of certain policies have been just rosy for a large section of Americans, is naive. To try and dismiss their views and blame them for being unknown puppets of Russia, is cruel and wrong.
note: I am not suggestion that Russia were not involved in some way in the US election.
Like Hillary being the worst candidate in a lifetime.
Would a good candidate brag about grabbing pussies, and attack a gold star family?
[1] I wouldn't say "won" but I would say "definitely helped" - there are a large number of other forces that contributed much, much more to the GOP win than Russia.