I think depending on your viewpoint, this could be considered in two ways.
1. It was clear and obvious the payoff and coverup was meant to deceive Mr Trump's wife and was thus a personal affair and hence not criminal.
2. The parties involved realized the two stories would negatively impact a campaign which they did not think they could win. hmmm ... if they didn't think they could win why would they care what the impact would be?
Regardless the parties involved may have argued the case from two directions. Was it a campaign contribution or was it personal? It could only be considered a campaign contribution if the payoff was meant to deceive the public in the hope of winning the election. Since they did not believe they would win, they would have argued it was not a campaign contribution. In fact I believe every legal expert I heard stated it would be a campaign contribution if they expected the printed stories to negatively impact a winnable election. Since they did not think they could win, they would argue it was not a campaign contribution.
I think it is clear from the filing, the SCO believes it was an undeclared campaign contribution which was covered up at the direction of individual #1. However, consider this argument. Mr Trump thought he would not win. So it would stand to reason he wouldn't care if the stories came to light. In fact, if the stories were printed he may have expanded his voter support (consider the Axios video which did not negatively impact his base) and won the election. Instead he opted to hide the stories. Why? to prevent emotional trauma to his wife.
OK OK ... now suppose SP Mueller reports Mr Trump has allegedly committed some crimes. Now we come to the crux ... does DoJ file criminal charges against a sitting president? or do we have to wait until he leaves office? Impeachment? Until there are at least 20 Republicans who will vote to convict, that would be pointless.
ignorance is the enemy
without equality there is no liberty