didn't fail because it had 2 permanent divisions of 8 or forced rivalries (to a degree). The WAC failed with 16 members because nobody (especially the older WAC members) liked the idea of dividing up into pods (WAC labelled as quadrants) and have 2 rotate every 2 years.

Quadrant 1: Hawai'i, Fresno State, San Jose State, San Diego State
Quadrant 2: UNLV, Air Force, Colorado State, Wyoming
Quadrant 3: BYU, Utah, New Mexico, UTEP
Quadrant 4: Tulsa, TCU, SMU, Rice

At the time Quadrant 1 and 4 all had 4 schools that were either already rivals or could easily become rivals over time. Quadrant 2 had 3 schools that were already rivals to a degree with UNLV being the odd man out. Quadrant 3 was essentially made up of 2 rivalries which I guess was okay since those 4 schools had not developed any strong consistent secondary rivalries with any of the other members. The BYU-Hawai'i rivalry might be the only exception, but I got the sense that both schools didn't exactly view the rivalry in the same light.

WAC set it up that Quadrant 1 was always a member of the Pacific Division and Quadrant 4 was always a member of the Mountain Division with the other 2 quadrants rotating between the divisions. In addition to the rotating pods, the other factors that influenced the failure were the fact that the conference covered 4 time zones, travel costs, and lack of revenue.