The "Trump Russia connections" storyline actually
originated from a small neoconservative clique in Washington. They were pushing antiRussian policy long before the 2016 elections- the Magnitsky Act, fighting ISIS in Syria, even tried to weaponize
gay rights as a way to condemn Russia. They badgered Obama for coordinating with the Russian military against ISIS in Syria. They found Clinton to be a reliable conduit for their foreign policy brand, and Trump to be an existential threat to it. It's hard to pinpoint exactly who this came from, but it clearly was consistent with their foreign policy views.
The Trump-Russia conspiracy theory is a madeup fabrication. It is a total falsehood. It's a hoax. Somebody made it up, and then news organizations mainstreamed it into the American conscience. None of this was an accident. None of it was an innocent mistake. Just like WMDs in Iraq, and the news cycle's abject failure in reporting that episode, this was done to advance neoconservative goals, like sanctions with Russia, escalated tensions, a new nuclear arms race with Russia, bigger military budgets, a litany of proxy wars (Syria, Ukraine, Iran, Venezuela) that could trigger a wider conflict. It allowed everything to be framed in terms where Vladimir Putin was basically the antichrist. It allowed any move away from a confrontational stance by Trump to be cast as 'weak', 'returning the favor' to Putin, being a "traitor" again. I remember very clearly when Trump was talking about pulling troops out of Syria, people immediately jumped to how it benefits the Kremlin, what a gift to Putin it was, etc. There was a #treasonsummit hashtag for the meet in Helsinki. It's a really simplistic and destructive worldview.