True, but those conferences have all expanded into super-conferences and now they each have many more basketball games that need to air somewhere.
Big 12 - added a net gain of 6 teams (+8 -2)
B1G - added 4 teams
ACC - added 3 teams
SEC - added 2 teams
Given that Fox has a contract with the two conferences who added the most teams (Big 12, B1G), they probably have all the content they need without the Big East. The net gain of 6 teams in the Big 12 plus the 4 teams in the B1G = 10 new teams under the Fox basketball umbrella, which is essentially the size of the Big East (minus one).