Is it really easier to believe that Russian bots are behind the lion's share of this content rather than other westerners?
The fringe is emboldened and encouraged and given an artificial air of legitimacy. The challenge or alternative viewpoint is suppressed.
It is still psychological warfare and the key point isn't really the individual composing the post.
Though in all fairness - based on the articles about the IRA and the experiences I've had I do think that that they have individuals posting and writing their own content.
(for those that haven't read about the Internet Research Agency yet: https://en.wikipedia.org/wiki/Internet_Research_Agency)