I don't know why car jacking stopped in other places, but in Maryland, it stopped because they increased the penalty to life in prison with the death penalty being possible.
What happened in Maryland was that in Columbia, MD (a wealthy crime free county of about 200,000 that averages 1 murder a year) two black men carjacked a woman and her baby. The woman did not want to leave the car without her baby, so she hung on, got her clothing caught and was dragged for about 1 mile and died, the car jackers noticed they had a baby on board, so they rolled down the window and gave the baby the heave ho out of a moving vehicle.
People (left, right, center, liberal, moderate, conservative) got really mad and made carjacking a crime almost equal to murder one.
That is when car jacking stopped in MD and not because of concealed carry.
In other states the carjackers got frequently met with the barrel of a big gun. Prior it was easy theft until it began costing the assholes their precious little lives.
The western end of Maryland is beautiful, but your gubmit is as far left as it could get. Hard to compare Maryland with any state except maybe Minnesota. Unless MD was executing them 30 minutes following trial, I doubt jail scared them much. Maybe the carjackers didn’t understand CC recip laws and just weren’t sure someone they tried to jack might be from a CC State like Florida or Texas and just might be armed.