My good friend lives in Pasadena, and he said it's just straight-up USC country ... like as extreme as Georgia being that much more popular than Georgia Tech in Atlanta. I get there are always complications and everyone loves the Rose Bowl in theory, but it actually blows my mind that UCLA has NEVER gotten its act together to build a cool stadium with a relatively small (50k or so) capacity near its beautiful campus. With absolutely zero traffic, you are still asking students to go 40 minutes or so to get to the Rose Bowl, and it can be over an hour with bad traffic. What would our attendance be like in Bloomington, if ISU happened to be a powerhouse?!
It's always surprised me UCLA hasn't leaned into being a more geographically oriented team rather than fighting to represent all of LA ... like a Cubs/Sox setup for LA's college support. From what I have heard, UCLA's campus is in a much better area, and it could have developed a reputation over the years as being "the team of the coast" or something like that and extend its fandom territory up north of LA more.