The Big10 has agreements with FOX, NBC and CBS as part of their existing deal for a 16 team conference.
If the Big10 would add Oregon, Washington or any other teams, where would those games be shown on linear TV? One of the Big10's existing partners would have to provide the linear timeslot. NBC Universal has USA and CBS has TBS/TNT.
Otherwise Oregon, Washington and the other 16 Big10 members are pushing the additional Big10 inventory to BTN, Peacock or Paramount+.
Big12 would seem to have a similar challenge in adding the corner 4. Obviously ESPN has a need for a late Saturday game, but would FOX after to a pro-rata and put a Big12 game or 2 on FOX. If FOX doesn't want more Big12 content, then that opens the door for Yormark to speak with Apple,.Amazon or a Big10 partner in NBC or CBS.