I've seen people discussing distance, etc., but if there's a time effect, why does it suddenly end when he's dead? That's not explained as far as I saw.
Kilgrave's power is dependent upon his continued shedding of viral matter absorbed by people in his vicinity. I suspect this is a media translation issue, incorrectly depicted by the production.
Like most Hollywood productions, when the villain or alien control system are destroyed, people are released from the control even if that flies in contradiction of the condition's previous parameters.
- Kilgrave's powers were derived from his original power set shown in the Alias comic. In the comics, Kilgrave's power is a physical one (biological pheromones) linked to his vocal commands.
- The Netflix televised version changed his powers linking it to viral shedding infused in the air around him, giving him control of the minds of people who heard his voice.
Thus the simplest explanation is upon his death, his viral shedding ceases and slowly people should lose their compulsion to obey him, depending on how long they were exposed to his power.
- The longer their exposure, the longer it takes for them to return to their normal thinking process.
- I also suspect, the closer you are to him, the more powerful his abilities are due to the proximity to an increased number of viral particles. Think of him having a cloud of particles around him extending to his maximum range.
- If a space is closed, it could intensify the effect since the wind, air conditioning or other air movement might thin the concentration of particles.
Scientifically speaking, if a person has been exposed to his power right before his death, unless they were conscripted minutes before, they should be following his last instructions for a least a few minutes. Since we don't get to see much of the people after Kilgrave's death, we aren't sure how they were really affected once he died.