Kidnapping a wealthy businessman turned out to be Kelly's downfall and landed him in Leavenworth and eventually Alcatraz. Despite his fearsome reputation, it doesn't sound like Kelly was very scary in person. He certainly didn't scare his victim much. Even while blindfolded, the victim managed to memorize a lot of ambient sounds, count and remember the number of footsteps from one room to another in the hideout, and leave his fingerprints everywhere. This was all quite helpful to the FBI and entitled Kelly to a lifetime of free room and board after he was apprehended.
Lots of lessons to be drawn here. Crime doesn't pay. Don't get mixed up with the wrong women. Marketing isn't always the truth. And on smaller scale: Never kidnap anyone smarter than you.
Words to live by, indeed.