We should first reference that people who successfully manipulate others often tend to pick targets that are much easier to manipulate. This happens in politics all the time. A person can get involved and reference things people agree with. That builds up faith or confidence for you with that group. Then you sprinkle in fakeness or lies, and since you already have them buying that you believe as they do, they are more likely to believe you.
Yet in the real world, being manipulative takes more creativity and targets are sometimes hard to spot. The hardest to manipulate is a generally curious person, as they will never truly believe you unless they do research first. Yet easier targets can be taken advantage of often. That is why this is one of the most toxic personality traits. Those who were manipulated will naturally never want to be around the manipulated again. That makes this one of the few things one can do that, if caught, instantly ends any conversation or relationship for most.
Your parents may have prevented you from hanging out with a specific friend. They might have even encouraged you to find other friends besides them. If this happened, they likely saw how that friend was changing you for the worst. As we age, our parents are not there to spot things and keep us from bad friends. We have to know how to do this for ourselves when we reach adulthood. Yet that is not always an easy thing to do, as some toxic people may not present as technically “toxic.”
Rather, they will appear normal yet slowly start to affect you. While family and friends can see the clear change, it is not always possible for you to see it for yourself. Truly, one of the most toxic personality traits is the ability to change others to bring the worst out of them. This is done for a few reasons. First, to make you act wrong enough to get others to say something to you about it. Then to use that to fuel wrongness in other ways, allowing them to manipulate you. See? It all works together for toxic people. They are like an infection while these traits are the symptoms. Remove the infection, get rid of the symptoms.