The issue is not fairness to the Democrats or whether the outcome of the election was influenced or changed. There is a strong consensus within the intelligence community (both CIA and FBI) that Russia was behind the attack, this is not in question.
The issue is that a foreign power interfered in an American election and the real question is were the Russian asked by the Trump campaign to do so? What did the Trump campaign know about the hack and when did they know about it? If any of this is true a foreign power will be able to continuing influence over the American government. Congress needs to investigate this immediately because under the Constitution it their job to do so. Congress has not been doing its job on many fronts, so I doubt this is going to happen.