For some reason that came into my mind today. And it intreated me. Why does it happen so easily?

because, contrary to popular belief, humans are the stupidest creatures alive

True I agree with you but still. There are some that are smart and so that can change a persons mind.

Humans are easily manipulated because they have a tendency to act on their emotions, even the most logical person cannot escape their own feelings. This allows intelligent people to act on their feelings, giving them information that will tip their feeling a certain way, allowing the manipulator to achieve their goal. Humans manipulate each other without even trying, merely by being around another person, you are, in a way, manipulating them.