Consider if it were your employee that was injured. You as an employer had purchased insurance coverage for your employees. Then an employee is hurt in a wreck and the insurance company of the owner of the truch that hit you paid your employee. And your insurance also paid your employee's bill.
Now your insurance company sues your former employee and the headline says Conservababe sues former employee. hu
It is pretty common in law. One can not make two insurace companies pay a person for the same damages.
It would be like buying two insurance polices on your car. If your car was totaled in a wreck you would get two cars. The law generally does not allow that.
Take it one step further to illustrate the double payment, assume that the trucking company and Walmart had the same insurance company. The insurance company paid twice. Once through Walmart's employee health plan and again through the trucking company's liability plan.
Since there wasn't a single insurance company involved, Walmart's employee health plan is due reimbursement from the trucking company's liability carrier, or in this case, from the settlement.
BTW, what is missing from the story is how much the lawyers took from the settlement. In a just system, the Walmart health plan would have been in-line for payment before the lawyers.