Even if Disney had liability, they would have an indemnity clause that would require the vendor to indemnify Disney for any and all liability resultant from the vendor’s operation.
So they sue Disney and Disney just tells the vendor to pay their attorney fees and any award.
They’ll go after the deepest pockets too. In this case likely the sponsor as well as the vendor. Did Disney sponsor a vendor/venue who’s safety precautions might have lacked seriously enough to cause death? It goes on and on.