A lot of that all-important Count One depends on showing they were actually acting as agents of a foreign government rather than just being foreigners acting for their own reasons, and whether public statements in a free-speech society are actually 'Interference in an election.' I suspect they may have to put on evidence they don't want to reveal to actually close the deal on showing that it was the actual Russian Federation government rather than just some troublemaking Russian dudes acting on their own.
The other two counts are more like garden-variety Russian gangster crimes (Wire fraud and identity theft) and only involve a relatively small subset of the Defendants, which will be much easier to handle since that kind of stuff has few novel issues and gets prosecuted all the time without the nationality of the Defendants mattering one way or the other.
I agree with you that the goal of the investigation is to prove that the Russian government coordinated to affect the election and the DOJ may be hard-pressed to prove it, or may not want to publically reveal what can be proved. But, in bringing criminal charges against individuals, Mueller has basically fallen back on FEC laws which are vague on allowable behavior. It appears his approach is to treat the social media offerings as an undisclosed contribution and he doesn't need to prove that behavior was state-sponsored to be illegal. Laws about foreigners being disallowed from voting and restricting their abilities to contribute to candidates are pretty clear, but the laws about what constitutes material and compensable support to a candidate leave a lot of grey areas. For example, foreign nationals are allowed to volunteer for candidates, but only in limited roles, and foreigners are allowed to participate in partisan political events, but are supposed to only speak about issues and not specifically endorse any candidate. Many of the FEC positions are similar to the rules imposed upon churches to attempt to maintain at least the appearance of impartiality.
I was speaking tongue-in-cheek about the foreign participants on DU, but I wonder if Mueller hasn't introduced a dangerous precedent. If you believe everything in Mueller's indictment, then there was a coordinated and well-funded attempt to create discord among American voters utilizing social media. However, based on the indictment, the attempted influence was bipartisan. So, if you extrapolate all the way to the Kremlin, Putin was just trying to make an acrimonious election even worse. And, if all that can be proved, we come to the conclusion that Putin is a tool. But any interference at that level is a diplomatic, not criminal, matter.
Mueller, by pursuing criminal charges, has introduced a new grey area. The whole world is on the internet so what constitutes foreign influence? Facebook pages, Twitter and message board posts? I'm interested in seeing how this is framed going forward, because at the moment Mueller has taken the position that we are all stupid and must be protected from BS on the internet, which is concerning from a First Amendment perspective.
