The reason the FBI did not alert the Trump campaign about Manafort is because they needed him to propel the Russia collusion narrative even though Manafort was hired primarily for the convention, Trump had pretty much wrapped up the nomination.
None of Manafort's crimes involved collusion, they all stem from work he did for Tony Podesta along with money laundering and tax evasion. Nothing to do with Russia, but the FBI senior leadership knew they could use that Russia collusion as a narrative to investigate.
It is also tragic that we live in an age when the FBI can frame you for lying because they believe another witness over your testimony even if you tell the truth. This is something that needs to be fixed!
