This is an example of the “just world fallacy.” There are many people so intelligent that they can cheat for so long and not get caught. Look at Michael Jackson. He died innocent in the eyes of the law.
Or look at the Zodiac killer: he’s still out there. Whole lotta people “trying to find the truth about that person”, as you say, and after decades and decades they got nothin’.
The world is not fair or just. Cheaters can cheat and get away with it, and they can do this in perpetuity. To think otherwise is to make a classic logical error.
If people want to know the truth about a person badly enough, they’re fucked. Because the truth is elusive. And the world ain’t fair.