It says right here in the article who paid for them.
You seem strangely hung up on this, while everything points in the direction of the Russians.
..but isn't the "shadowy Russian buyer" simply the bot farm who paid for the ads? Unless you know who funded said bot farm (which may well be Russia..or it may well push ads from groups/people from all around the world (be it to push stories about political parties..or tell us on a daily basis how "Kim Kardashian Just Shaded Taylor Swift Again With 16 Words").
I wouldn't say I'm hung up on it. I just get increasingly aggravated with supposition, possibilities and opinion replacing cold hard unbiased facts (pointing "in the direction of" isn't good enough).
A true news source shouldn't come down on either side or slant in one direction over another without clear, proven, evidence to back it up.
I won't post any more as I'm clearly a Russian spy working directly for Putin.