The CIA and the military/security complex need an enemy in order to justify their huge budgets and unaccountable power. Russia has been assigned that role. The Democrats joined in as a way of attacking Trump. They hoped to have him tarnished as cooperating with Russia to steal the presidential election from Hillary and to have him impeached. I don't think the Democrats have considered the consequence of further worsening the relations between the US and Russia.
Public Russia bashing pre-dates Trump. It has been going on privately in neoconservative circles for years, but appeared publicly during the Obama regime when Russia blocked Washington's plans to invade Syria and to bomb Iran.
Russia bashing became more intense when Washington's coup in Ukraine failed to deliver Crimea. Washington had intended for the new Ukrainian regime to evict the Russians from their naval base on the Black Sea. This goal was frustrated when Crimea voted to rejoin Russia.
The neoconservative ideology of US world hegemony requires the principal goal of US foreign policy to be to prevent the rise of other countries that can serve as a restraint on US unilateralism. This is the main basis for the hostility of US foreign policy toward Russia, and of course there also is the material interests of the military/security complex.