Tortious interference comes when:
1. There is a valid contract between Party 1 and Party 2
2. Party 3 knew of the contract
3. Party 3 engaged in intentional acts designed to disrupt the contractual relationship
4. There is actual disruption of the contractual relationship
5. Party 1 or Party 2 sustains damages as a result of the disrupted contractual relationship.

Here the Big XII has a contract with Texas & Oklahoma. That contract allows them to leave the conference with a payout. If ESPN takes action to disrupt that contractual relationship - e.g. destroys the conference by encouraging other conferences to take all the other teams away - and as a result, Texas and Oklahoma don't their exit fee then that (or something similar) could be the basis of the claim.

Also worth noting is that if the Big XII dissolves, ESPN claims it is off the hook for the remaining $500 million, and there is evidence to show that ESPN helped orchestrate the downfall of the Big XII, then this could be a claim of the breach of the covenant of good faith and fair dealing, which basically requires the parties to a contract to perform the contract in good faith. A party can comply with the letter of a contract while still breaching this duty.