It doesn't seem very logical to dismiss evidence from an organization because of a few mistakes. Consider also the wealth of things they got right, some of which may never be made public.
Firstly, there is no evidence from the CIA regarding the election hacks. There are anonymous sources who claim to work with/in the CIA and/or have information from the CIA.
Secondly, I'm not saying to outright dismiss it, but, that you need to frame the information in the context of their success rate. (and, no, you don't get to consider secret unknowable wins in that calculation)
The alternative position is the one where we first collect all the analysis and evidence and context and present it to you so that you can say you knew all of that all along and didn't mention it because it was so obviously flawed.
In addition to being frustrating to deal with, that latter position is an effective way to shoot down any common-sense argument, from "vaccines don't cause autism" to "men really did land on the moon" to "9/11 was not an inside job".
I clearly see goals and actions, and I attribute them to Russia, because they will benefit a lot from resolution, but I have trained eye because I watched how Russians are working in Ukraine at time of Maidan.
As far as Russia benefiting from the election, what benefit do you think Russia gets out of the situation that isn't just a large, common benefit that could be equally attributable to anyone?
EG: if you say Russia wanted Trump elected because Trump would be a better friend to Russia that doesn't convince me that Russia was involved in that at all. Fixing Russia/US relations has massive, global benefit, it seems equally fair to say that Belgium hacked the election (whatever that means) to prevent Hillary from ending up in a nuclear war with Russia which would obviously be bad for, well, everyone (to be crystal clear, i'm not saying this is true or that I believe this would have happened).
My point isn't that everything I'm saying is correct, merely that there are lots of equally plausible scenarios here.
I also unable to see how Russian-US relations can be better than now. Russia captured Crimea, while USA and Britain are ignored their obligations. It's looks like a gift. Yeah, sanctions can be canceled, but even if not, sanctions are doing very minor harm in compare to gained benefit: Russia now controls Black Sea and can intercept rockets launched from Turkey, so USA bases in Turkey are useless now. Also Russia prevented Shell from pumping of natural gas from Sloviansk (their second goal after Crimea) to Europer, so they saved lot of money on that war.
Also chemical weapons in Iraq.