I think the Democrats are pushing this bogus story because of Iran. Russia has reappraised its relationship with Iran in light of all of the money that Obama gave it. The only way to re-isolate Iran and keep it from going nuclear would be for the US and Russia to collaborate on this project. Otherwise we will see Iran become the dominant power in the Middle East and possibly attack Israel as well as Saudi Arabia and other countries.
The Democrats hope to intimidate the Trump Administration from getting too close to Russia because any collaboration will be seized upon by the Democrats and MSM as evidence of a conspiracy.
Democrats are children in a sandbox building sandcastles. Meanwhile we have a president (who the dims hate) who builds real castles, lots of them.