I've been trying to look at this thing as objectively as I can, to try to figure out how it all could have occurred, and who's mendacious and who's merely gullible.
It's a puzzler.
Was this a matter of a campaign and an administration cynically trying to manipulate the results of an election? Or was there in fact genuine concern that the Trump campaign, and even Trump himself, had been penetrated by Russian intelligence? I understand that conclusion contradicts the standard trope that the simplest explanation is usually the correct one. (Trump's kid's meeting with the Russian who claimed to have "dirt" on Hillary, for example, almost certainly wasn't collusion but naivety that was never followed up upon). But Trump WAS an international oligarch, and did have business interests in Russia - is it possible that the administration and American intelligence professionals had genuine worries about a potential Manchurian candidate, and were suckered by the Clinton cabal, or both suckered by someone else?
Did Steele present his dossier with any imprimatur of reliability, or did he just throw a bunch of raw shit together with no vouchsafe, and let his dirty clients do with it what they will? Did Steele's past activities as a spy, known to American intelligence, cause the CIA/FBI to attach possible credibility to the information notwithstanding the tainted nature of the dossier's champion?
What seems most likely to me is that the Hillary campaign was the true evil actor, not necessarily the Obama administration and our professional intelligence agencies. Clearly, I think, the administration became aware of the dossier because the campaign leaked it. The administration seemed both breathlessly worried about the veracity of the evidence pointing (circumstantially) to a mole in the Trump campaign (or Trump's vulnerability to blackmail), and petrified at the thought it might have to do something about it. It bent the law to obtain the FISA warrants, and had other evidence of Russian election-related meddling/infiltration, but made no attempt to alert local authorities concerned with election security. What explains this combination of legally reckless yet cautious behavior, especially if the Obama administration, like just about everyone else, was confident that Hillary would win?