We don't talk of a conspiracy to win an election if the suspect activity includes only candidates and their handlers working privately to develop effective strategy. We do talk about a conspiracy if the resulting action involves stealing the other team's plans, spiking their Whiskey Sours, or other exceptional activity. When a conspiracy cause's some outcome, the outcome would not have happened had not the particular people with their particular inclinations come together. Conspiracy theories may or may not identify real coteries with real influence. Personalities, personal timetables, secret meetings, and conspirators' joint actions, claim attention.
Institutional relations drop from view.
The personal actions culminating in some event do not serve as explanation. The theory explains phenomena via roles, incentives, and dynamics of underlying institutions. An institutional theory doesn't ignore human actions, but the point of an institutional explanation is to move from personal factors to institutional ones. If the particular people hadn't been there to do it, most likely someone else would have. An institutional theory of Irancontra and the October surprise would explain how and why these activities arose in a society with our political, social, and economic forms.