I was in a situation with some similarities once. There were several factors that protected the person:
1. They were charismatic, charming, and likable. Fun to be around. But they also had an angry/mean side that started to come out when things weren't going their way. People around them were trained to do things that brought out the fun side and avoid things that brought out the mean side.
2. They built their circle out of people who were impressionable and had a lot to gain by being part of the circle: Early career people, people desperate to climb the ladder, and people who wanted a lot of praise. There was an implicit understanding that as long as you didn't rock the boat, you just had to put up with everything for a couple years before pivoting to your dream position. If you exposed the person, your own resume might look questionable, so you had to go along with it.
3. Anyone who actually questioned them was marked for destruction. They would do everything in their power to discredit you, undermine your work, interfere with things you were doing, argue against promotions, and otherwise bring your career to a halt. It was all done out in the open, as a warning shot to anyone else who questioned it. People notice.
For a famous example, look into the Lance Armstrong story. He didn't just cheat, he tried to destroy the lives of anyone who might get in his way. He's a charismatic celebrity, so to this day he continues to whitewash his history by being nice and likable. Even after everything that has been revealed and admitted, people will still jump to his defense by substituting a lesser narrative and defending that. The common defense is "Yeah, well, everyone in cycling does doping!" even though doping is one of the least concerning things Lance Armstrong did.
Another upsetting factor is that people develop parasocial relationships with these grifters and will go to great lengths to dismiss or downplay their problems. Look at the recent issues with Andrew Huberman for a good example. Not only has his grasp of science been called into question on many topics, but his personal life has been exposed as being quite different than the ultra-righteous fatherly figure that he plays on his podcast. Yet despite this, people who love his podcast will rush to his defense and try to downplay the problems. Like the above story, people try to downplay the revelations about his personal life as if he made a mistake and "cheated on his girlfriend", when the actual allegations are more far-reaching and establish a chronic pattern of dishonesty.