"They" are the midwest transplants living in SoCal that Mach referenced. If it was about grabbing the transplant market, there are a ton of transplants (both permanent and winter visitors) in the 5th largest media market in Phoenix.
Somewhat confused by your point that it's not about viewership, but your example is about viewership.
Hey, I'm in San Diego and I get the BTN. It comes with my sports package. My point what is the marginal increase of B1G football/other sports does adding $C/UcLA bring from SoCal. If you were a fan before, you were already tuning in. Are the fickle eyeballs of the LA schools worth that much for the 16 games? I doubt that SoCal viewers are going to pivot their entertainment time to Rutgers/Northwestern 9 am kick just because it's a conference matchup. The entertainment time is important as you need to compete against non-sport LA activities (huge), two MLB teams for Sept and maybe Oct, two NFL teams on generally the same schedule, two NBA teams that start in October, two NHL teams that start in October.