The difference is a simple one. The multiple experts in the Iraq fiasco consisted of intelligence analyst in 5 countries all reading separate intelligence reports from their source in Iraq. Then used each other as corroborating sources.
But after the fact it was revealed that they all were talking to the same guy.
This is 3 different companies, looking at multiple hacks, and an entirely different guy, a British professor, looking at a separate data set in Germany, and drawing the same conclusion.
If you can't see the difference I don't know what to say.
Perhaps it's not what I can't see, but what I do see.
It's not so simple as you say.
The administration can require particular results of contractors.
I've seen this first hand IRL.
And even these contractors are only speculating that Russia is a likely candidate.
No one has presented any named expert who says more than this.
Yet it's taken on faith that the politically preferred inference is fact.
The more important question is....why do this?
We've been engaged in cyberwarfare with many countries for a long time now.
It's even likely that Putin is correct in his accusation that we've meddled in his
political affairs too. I speculate that Hillary & fans want to portray what is normal
as something new & threatening because it's so effective at whipping the masses
into a supportive frenzy. The problem with this is not the inherent dishonesty,
but the risk of increasing conflict with Russia. That would lead nowhere good.