In the end he was caught because his van was identified and because "One of his sons had revealed to his then-girlfriend that his father had placed a bomb in Harvey's." I always wonder at how criminals that otherwise might seem movie-like masterminds are caught as a result of mundane mistakes and outright stupid moves like this. You would think if you are going to bomb a place, the first thing would be to not talk ab…
As always, with any crime, the more people involved, the greater the possibility that human factors will sabotage the operation. The perfect crime has one perpetrator. It is also why its fascinating that people will believe in conspiracy theories that supposedly involve tens / hundreds / thousands of people. Theories that we faked the moon landing always intrigue me. Or that the earth is flat.
For sure it's true that a secret can be kept by three people if two of them are dead. But there are clear cases where large groups of people have been able to keep secrets as well, or at least keep them from spilling out into public awareness.
I'd bet that for most crimes, the secret isn't kept, and there is someone else out there that knows who did it, who simply doesn't tell law enforcement. And yet most serious crimes aren't solved.
Humans have a real need to tell other people personal things, even to their own detriment. But sometimes things stay secrets even if tons of people know about them.