The CIA doesn't just issue blanket statements without proper information to back up their analysis. If they say that Russia interfered with the election, then that country probably did. We need further investigation to see exactly how big Russia's role was, and determine if we need to do something to contest the results.
F.B.I. Director James B. Comey with his "Bogus" reopening of Clinton's e-mail "investigation" of "nothing new" during the actual voting process absolutely "Manipulated" the 2016 Presidential Election out come.
Comey was used as Putin's "Puppet" and it worked exactly as Trump/Putin planned.
The 2016 Election was Corrupted by the combination of both Russia, and the Treasonous politically motivated abuse of power by James B. Comey.
It's debatable whether or not Russia's meddling in the election had a real impact on the outcome. Given that they hacked and leaked emails that put a bit of a bad vibe on Clinton and the democrats, I'm inclined to think that there was an impact, especially with how close the vote was in many states.
If Russia helped Trump win the elections, then the CIA and the government should review their security system. As did the NSA who falsely claimed to not be spying on us, the CIA could very well be telling us lies because a Trump government wouldn't be good for them.
But the CIA most likely has a reason to say something like that.
Ultimately, only Americans could vote for Americans. The Democrats have made it very clear that they don't think that voter fraud is a problem in the United States. In addition, the Russians would not want to help Trump win the Presidency. Clinton would have let Russia get away with a lot more stuff than Trump is going to allow.