I made sure he died is making sure that the action of dying was completed. In that sense it sounds like you contributed to them dying. E.g. a mobster telling his boss he made sure someone died.
I made sure he was dead, is confirming their state of being as dead. E.g. a professional would ensure someone was dead before they’re cremated.
There is a lot of nuance in there though. E.g. a mobster might also make sure someone was dead after e.g. shooting them. (But again it’s checking their state of being rather than ensuring their act of dying was complete. I.e. finishing them off)
It’s an action vs a state of being.
I made sure he died is making sure that the action of dying was completed. In that sense it sounds like you contributed to them dying. E.g. a mobster telling his boss he made sure someone died.
I made sure he was dead, is confirming their state of being as dead. E.g. a professional would ensure someone was dead before they’re cremated.
There is a lot of nuance in there though. E.g. a mobster might also make sure someone was dead after e.g. shooting them. (But again it’s checking their state of being rather than ensuring their act of dying was complete. I.e. finishing them off)