Mujahedin Khalq; A proxy force

In the 1970s, however, MEK was responsible for the death of three American officers and three civilian contractors in Iran. The group also voiced significant support for Iran’s taking of hostages during the Iranian hostage crisis, and some reports indicate that members of the group celebrated the 9/11 attacks, though the organization publicly condemned the attacks.MEK has conducted a number of other terrorist attacks as well, but most have been excused because they were directed against the Iranian government…

… There is no history of such behavior even when the country was militarily much weaker and politically unstable. Thus, to best answer the question is to identify those who would benefit the most from a confrontation between the U.S. and Iran. Clearly those who have the most to gain from such a clash are Israel and the Iranian opposition, particularly the Mujahedin Khalq Organization (MKO) aka MEK/PMOI..