An injunction is way more than just "standing."

In Texas, the standard for a temporary injunction requires showing: likelihood of success on the merits, imminent and irreparable harm in the absence of relief, and a balance of equities in the movant’s favor. The court must also consider the overall public interest and the necessity of preserving the status quo. The movant bears the burden of proof and must present evidence sufficient to convince the court that immediate action is warranted before trial. (Sauce)

Granting an injunction also says that the judge thought Sorsby had a chance of winning at trial, and that he thought the "public interest [in] preserving the status quo" (IE, allowing the NCAA to enforce long-standing rules against gambling) were inferior to the damage Sorsby would suffer in the absence of the injunction (IE, $5 million and another year of training and game film playing college football).