The essence of the controversy was whether the FBI had legitimate legal grounds to investigate one of Trump's campaign advisors. The Republicans claim it didn't, but as Schiff's document proves, it had significant grounds to do so.
It's important to note that the investigated advisor, Carter Page, hasn't even been charged with a crime and that the issues involved have nothing to do with Trump's people who have been indicted and arrested. Nor does it have anything to do with Trump's possible unlawful activities, like obstruction of justice and money laundering, nor the possible crimes committed by his son and son-in-law.
Trump's response to the damning memo was nothing short of fraudulent propaganda. In an interview on sympathetic Fox News, he claimed Schiff's document vindicates him, when it does the opposite, and that it proves what he's been saying is correct, when it proves he's been lying.
With Trump's support in polls now at an all-time low, it's pretty obvious that he's no longer trying to convince the significant majority of Americans who know he's a habitual liar, corrupt, and incompetent. He's just mainlining lies to his supporters, hoping they won't read or view actual news to learn the truth.
Most Republicans in Congress continue to support him, at least publicly, apparently thinking that handcuffing themselves to a toxic President will somehow improve their chances in this year's midterms. It's an inherently losing proposition that they'll only be able to pull off by obstructing justice, cranking out deceptive propaganda, and hoping Russian hackers hand them another victory.