Because Rutgers was entrance into the NYC market. They were/are continuous, AAU, and just merged with the med school. Rutgers WAS about subscriptions. Remember, Fox just purchased controlling interest in the YES network. Just like ESPN leveraged it's network with The SECN, Fox could/did the same with the BTN. Rutgers was a great addition for the Big10 alumni in NYC, just like UMD was for DC alumni.
Since the Big10 gets money from different aspects of it media, they need names for the tier 1 negotiations. People watch Oklahoma football and Kansas basketball. They will be on ABC/Fox broadcast network channels, not on the secondary channels. Imagine Michigan and Oklahoma playing in October. The revival of the Nebraska - Oklahoma series. They could, potentially, have the Red River Shootout every other year! Throwin in Kansas BBall games against Indiana, Michigan State, Wisconsisn, and Maryland, you've got a pretty good lineup there that would make money for advertisers on winter Saturdays. The markets aren't great, but Kansas has pull in Kansas City and Oklahoma has pull in Dallas/Fort Worth.
Obviously, UNC and UVA would be the main targets, but they seem to want to stay in the ACC. I have been a very large proponent of VT and UConn to the Big10, but I don't see that happening quite yet. Since we are playing with the scenario of the Big12 GoR having a loophole, OU and KU seem to be the most attainable.