HP Salem which is a HP from over 15 years ago, never betrayed us in anyway. I have explained on this.
Salem was loyal, but he disobeyed repeatedly HPS Maxine's wise orders on two things; one thing was to not publicly expose himself and to not issue threats to enemies of JoS on a camera, and the second was to stop doing dangerous drugs, which he did as part of his profession.
It didn't take long before he paid the price of this disobedience which caused him increasing damage and eventually this made him progressively lose his sanity. Salem didn't care and played it stupidly, which is typical LHP behavior at the time, where people didn't understand what they were doing.
Eventually, these two things coupled with a few other personalities faults were his undoing and downfall. Yet this was not related to any form of betrayal or any "betrayal" that was in anyway intended. In other words he never gave in to the enemy or whatever.
In his mind he could not understand what he was doing was actually bad, despite of it being obvious. He denied the signs of damage and decay taking place. The Gods tried to also warn him to no avail, until he completely lost it entirely.
A combination of over egoistical perception, delusion based on drugs, and also coupled by what we have to admit was an uncontrollable zeal for JoS that he could not control based on wise counselling and learning where to put the breaks, did cause him a major downfall.