But I can't see any reason to think that Russia would be the main actor in the "false-flag/astroturf space". I mean, it's hard not to think everyone with an interest in the outcome would be pushing here to get their interests served.

Certainly, the DNC emails seemed to demonstrate an interest in underhanded approaches (not that I'd discount a similar interest from the Trump campaign). And PACs that are actually independent would be jumping in the action, etc.