How Russia Helped Swing the Election for Trump

No, actually, Democrats and Republicans have used that over the years to suggest that Sanders had Communist sympathies and/or poor judgement, it was not a basis for attacks by Democrats (or anyone else, AFAIK) that his 2016 campaign benefited from Russian manipulation.

OTOH, his 2016 campaign (and Stein’s) was apparently a beneficiary of Russian manipulation (and I think Sanders has a acknowledged at least that the evidence suggests this), though information about that didn't come out in time for that information to be used in the campaign (and there's been, AFAIK, no indication or significant accusation of collusion on the part of his campaign, thogut Stein’s is a different story.)

Because Russia is a major regional power whose regional interests are frequently in conflict with the Western Alliance (both NATO specifically and the other Western European political and economic structures), which they've been trying to weaken. Their manipulation with regard to, among other things, Catalán independence, Brexit, and the attempts to weaken Clinton and boost Trump primarily, but also some other rivals (which seems to have been expected to fail in electoral terms but leave the resulting Administration weaker with deeper and more aggressive domestic resistance than without intervention) all fit into that pattern.

> Russia is a third world country

The (primary successor in interest to, at least) definitive second world country, actually.