Murderers and their Followers

I just finished reading the book "Helter Skelter" by Vincent Bugliosi, and I was amazed of the how the murders happened and the journey that had taken place throughout the trial. Charles Manson and his "family" lived on a ranch and most of the girls living there were no older than 20 years old. Manson had planned murders that were carried out by three women and one man on two separate nights. When it came to the trial the females and Manson were tried together and convicted of first degree murder and they recieved the death penalty. When it came down to the sentencing, the girls made Manson out to be a saint and said he had nothing to do with it. They were willing to take the fall for him when they were the ones manipulated. Some of the other followers picketed outside and carved symbols on their foreheads to free Manson.
What I don't get about the whole "Manson Family" is how someone can have so much power that people would do anything for him? These girls killed for a man that would have threw them under the bus the first chance he got. I don't understand how these girls could be so vulnerable that they would do anything for him. The protesters outside the court house made Manson to be such a good person that other people started to believe he was innocent and started wearing shirts that said "Free Manson". The prosecution tried so hard to keep the jury isolated, but with all of the media it was hard to keep that isolation. I was very surprised to see that they found them guilty because the media could have persuaded them for a not guilty verdict. I think it is amazing to see how one person can be so influentual in someone's life to get them to kill.