While I found the series interesting, with fine acting, I can't rate it higher than a "1" when it comes to accuracy.
MAJOR, MAJOR SPOILER ALERT FOLLOWS - if you plan on watching "Trust" and don't want to read any spoiler alerts, please stop reading now!
The most notorious aspect of the kidnapping (other than the wealthy grandfather refusing initially to pay any ransom) would have to be the victim having his ear cut off, and sent to his family. In the real-life case, there's no doubt the kidnappers did the dirty deed; the victim, after his release, said so in an interview. Not so in the "Trust" version:
In episode 8, after a deal to pay the ransom falls through, the kidnappers decide to kill the victim. The teenage son of one of the kidnappers, hearing this, races to the cave where the victim's being held, frees him, and tells him to run away. The victim realizes running away won't work - any villager he came across would likely return him to the mafia kidnappers (as happens in a previous episode). So in a desperate attempt to save his own life, the victim begs the teenager to cut off one of his ears and send it to his family, to pressure them into paying the ransom. The teenager reluctantly obliges.
To change this major element of the kidnapping - from the kidnappers cutting off their victim's ear, to the victim asking for this to be done - is kind of like taking a real life case of a woman being kidnapped and raped, and changing this, so that in your fictional version, the victim asks for it!
Why would the producers change this element of the story - is it because the writers and producers did no research whatsoever? Did they feel that kidnappers cutting off their victim's ear isn't dramatic enough? Were they afraid of antagonizing the real mafia? ("I realize we're portraying the mafia as kidnappers and killers, but if we also portray them as mutilators, why, they might be angry at us! We better change that! I know, we'll have the victim ask to have his ear cut off!")
So if you want to watch some interesting fiction, this series fits the bill. If you want to watch an accurate rendering of the Getty kidnapping, look elsewhere.