A few disclaimers. Im not a believer nor super knowledgeable about any specific interpretation. There are many interpretations and here is one.

Hell is supposed to be bad because its disconnected from god. Before satan all was god and in withdrawing his being it made a second place. Also satan is immortal so its possible he can’t be killed which is why god was so worried about adam and eve eating from the fruit of eternal life. Eating the apple of good and evil allowed some of mankind to be evil enough to not be allowed in gods prescence so are in the only other place. Satan being powerful and there from the get go easily controls the place.