I know this is going to sound very politically incorrect - but I will venture to step into it anyways: let us say that a spouse comes to a point with their mate where they no longer have any interest in sex and they simply end that part of their relationship. Then, after a year or two of this, the other spouse goes outs and decides if there is no home cooking - they will get some fast food. So the offended spouse wants to hire a private investigator to nail the mate to the wall and provide evidence of the infidelity. What are the chances that the offended spouse will look at their own complicity, their own actions and their own role in helping to create this problem in the first place?
I suspect the Congress in their possible investigations would be in a very similar position. And I further suspect nothing good or lasting would come from it and it would be very limited to "getting the bastard" that their sights are set upon. And when a new bastard from their own party comes in and does the same thing they will not be as prosecutorial nor as judgmental and will tend to look the other way.