Yet maybe it was deliberate. It brought extensive focus on him again and at the same time on McCain's record, including much that is negative. Sure McCain was a POW. But getting captured does not make one a hero. And there is McCain's opposition to POW/MIA issues and his embracing his captors.
https://en.wikipedia.org/wiki/Doug_Hegdahl
This guy was a POW and was a true hero. He caused more damage to the Vietnamese army that many of the pilots.
“During his prison stay, Hegdahl sabotaged five trucks by putting small amounts of dirt in their gas tanks. After he was through with them, each of the vehicles had to be towed from the compound.”