in my opinion the possession by deva is due to some karmic account of that person with that deva .As per cause and effect law, there should be some cause owning to that person and obviously possession by deva is effect.Not centpercent true but may be of little worth of thinking.The responsibility of that kamma is of both.Unless we have some potential gathi of immoralty,the deva or anbody or even ourselves cannot possess.