Apparently not enough for not invading.
The CIA presented the evidence to the W Admin, and the W Admin was not happy with the presentation as it certainly did not hold much water. The presentation was tightened up a bit and then given by Powell at the UN. A good deal of the "evidence" consisted of a lack of documentation, which was actually technically true if held out of context of the fact the WMDs would have been useless by 2003 and just because there was a lack of documentation didn't automatically mean the weapons still existed. The CIA gave the W Admin a bit too much rope, but the source of the problem with Iraq was not the CIA. CIA enabled the W Admin, and it was the W Admin that wanted to invade Iraq.
The comparison of Iraq with Russian influence in the US election is folly. Iraq had no consensus that a war was needed or that there was a danger. In fact, there were a lot disputing this, from diplomats to intelligence. Russian influence is pretty much sold across the board as being fact among private and Federal cyber-security investigators
(and even Putin's useful idiot admitted that the Russians were behind the hacks). Unlike Iraq where the presence of WMDs was anything but certain, we
know that the DNC was hacked.
But yeah, I already know your rebuttal... Iraq. *rolls-eyes*