The story is a bit more complex. In the late 1800s (under their first president), Wheaton was rather progressive. The second president (son of the first) was a dispensationalist who reversed all of that progress and turned it into a conservative institution. Things have largely remained that way. Following WWII, evangelicalism as we know was born as a movement away from the fundamentalism of the early 20th century. This new evangelicalism, which concurred with the establishment of Fuller, CT, and the NAE, was somewhat more progressive than before, and during this time I think you could say Wheaton evinced a moderate evangelicalism. All of that changed after 1980 with the rise of the Religious Right, and things went downhill in a hurry with the appointment of Duane Litfin as president in 1993.