It’s the other way around. The Big Ten is looking for a different TV partner than ESPN.
FOX has the Tier 1 rights, so they will have the first right to choose the Big Ten game each Saturday, along with showing games on FS1 and FS2. FOX also increased their stake in the BTN and owns 60% of that network.
The Tier 2 rights is what looks to be going to CBS and/or NBC. CBS and NBC are looking for more inventory of games, especially on Saturday afternoons and sometimes Saturday nights.
This is not ESPN squeezing out the Big Ten. This is the Big Ten realizing they can get plenty of cash from networks outside of ESPN, and making the push to say that ESPN doesn’t own college football.