While there can be a silent period between a TBI/injury and seizures starting, older people (and children) have a higher incidence of epilepsy so unless it's correlated to damage they see, it could be from other reasons and focal/partial seizures are more likely than generalized seizures overall (different distribution of seizure types in pediatric population).

One of our kids has seizures so I knew enough after a while to not be surprised when my mom got them late in life. Seizures are more common than people seem to realize.