Not to get to detailed about the modified comparative negligence and this crash (it's something I deal with everyday) but chances are unless the driver of the van is found to be more than 50% at fault the family or estate will recover something from the Cowboys insurance. Even if they made an illegal left turn an attorney could argue the Cowboys driver had the last clear chance to avoid the accident and if it becomes 50/50 then (and I'm not as sure about Texas as I am Tennessee) the family of the deceased could still recover 50% of what would be owed to them if they were 0 at fault. Tennessee is a 50% bar state and Texas a 51. However some modified competitive states following the 51 rule allow you to still recover if deemed 50% at fault. Your recovery is just reduced 50%
All that to say, sometimes you are just buying a signature on a release to avoid litigation. For an origination like the Cowboys vs little family of 4, courts tend to side with the little guy