The problem is that does happen in real life. Intelligence services and organised crime work actively to hide their tracks. As do corrupt officials and some of the military.
We live in a society where corruption is rife and ordinary people are largely excluded from most major institutions ... That is the atmosphere that breeds these things.
My favorite way to cut apart those two is to ask: How many people need to keep a secret, how long and how perfectly would they need to succeed, and what motive do they have to do a good job?