The article states

"Court records show the landlord alleged more than $8,000 in unpaid rent, but ultimately reached an agreement with the tenants last May that no money was owed, the tenants would move out by January, and the landlord would make necessary repairs."

So I'm assuming the tenant didn't have an attorney and agreed to the deal in mediation which means the judge never even heard the case. The landlord's attorney likely knew they didn't have a case if what you said is true, and thus was willing to waive so much back rent on the condition that the tenant just surrenders the premises.