Universities that spent a century in one conference now change leagues in a way that ignores geography. The driver is the way television rights are packaged and sold.
Media rights are sold by the conference
Individual schools do not generally sell their football and basketball inventory alone. The conference negotiates a package covering its members and distributes the proceeds.
The value of that package depends on the number of attractive matchups, the size of the television markets involved and the national appeal of the brands included.
Adding a school that raises the package value therefore raises revenue for every existing member, which is the arithmetic behind an invitation.
Departures compound quickly
When a prominent member leaves, the remaining league's next negotiation starts from a weaker position, which reduces distributions to those who stayed.
Anticipating that, other members begin exploring exits, and a conference can unravel faster than its leadership can respond.
Grant of rights agreements exist to slow this, binding members to assign their media rights to the league for a fixed term regardless of departure.
Exit fees are a negotiated cost
Conference bylaws set penalties for leaving, typically a multiple of annual distributions plus notice requirements.
A school joining a more lucrative league can treat that penalty as an investment, since the difference in annual revenue may recover it within a few years.
Disputes over these amounts often settle privately, which is why announced exits and final payments rarely match the published formulas.
Travel costs fall on athletes in other sports
Football and men's basketball generate the revenue, but realignment applies to entire athletic departments, including sports that play midweek schedules.
A volleyball or baseball team crossing several time zones for conference play absorbs missed class time and longer recovery windows.
Universities address this with charter travel and adjusted schedules, which raises costs that the new media revenue is expected to cover.
Postseason access shapes the incentives
Selection for national championships depends partly on schedule strength and on automatic bids tied to conference championships.
Belonging to a league whose champion receives favorable access is worth more than the raw distribution figure suggests.
As championship formats change, the calculation about which conference is worth joining changes with them, which is why realignment arrives in waves rather than continuously.
Each expansion of a championship field alters how much a difficult conference schedule helps or hurts a team's case, and athletic directors reassess their affiliation accordingly.