No, they didn’t. You can’t rig something that you don’t control.
There were 41 Democratic presidential primaries during the 2016 election season. With the exception of the Democrats Abroad primary, the primaries were conducted by state election officials. For example, the Alabama primary was conducted by the Elections Commission of the office of the Secretary of State. They determine the eligibility of voters, choose election officials, choose voting locations, count the votes, and certify the results. It’s ridiculous to contend that these people are controlled by the Democratic National Committee. It’s also ridiculous to content that the DNC could control the election apparatus in 39 other states.
Why is this important?
The Russian troll farms are hard at work on the 2020 election, and have been at it since mid-2018. (See Stop calling them ‘Russian troll farms’ by Joshua A. Geltzer at CNN.) On this particular topic, they are playing the long game, and here’s what it is.
They are pushing the “Bernie was robbed” story. They are saying that if Sanders does not win the nomination in 2020, it will also be because of the intervention of the DNC, the DCCC, the “establishment”, or some other boogie person. This will be used as justification for voting for Tofu Palin, writing in someone’s name, spoiling the ballot in some other way, or not voting at all.
There is also a “the Democratic candidate must be a woman” meme. If a male candidate is nominated, the trolls will be pushing the “vote for Tofu Palin instead” message.