I guess you believe they interfered in 16?
Not in a large way. Of course, any world leader, or any publication, or posts made on the internet, or anyone, can effect votes by the statements they made.
The Russians have not controlled any election in the U. S. during the 21st Century, or at any time that I know of. They just want us to think that someone controls the elections. And that someone can be anyone, including themselves. I typical tactic of those who oppose democracy. The best attack, is to suggest that democracy is an illusion. By arguing that elections are fraudulent, or a deep state is really running things, possibly as a result of an assassination. Lots of techniques, all involving the notion that a nation's democracy is an illusion.