In which way was Weis' contract structured differently? I really don't get it.
Under the contract the coach agrees to provide services in exchange for compensation. When the coach gets fired the school breaches the contract. The contract may or may not include buyout provisions regarding what the coach is owed on the remainder if he is fired - or what the school is owed if the coach leaves.
If there is no stipulated buyout the school presumably owes the coach the remaining money on the contract if they fire him. In this case, the coach still gets paid his salary as damages for breach BUT the coach then has the duty to reduce his damages by taking efforts to find new employment. Another alternative, if there is no buyout in the original contract, is that the two parties can negotiate a termination of the contract. Then the fired coach gets paid some stipulated amount which generally has no strings attached (this appears to be the case with Weis).
Here it seems the parties ended on terms (either through the original contract or an agreed settlement of Hoke's claim for damages by UM's breach) where UM owes Hoke a salary which gets reduced by his outside earnings over the next two years.