fearless public speaking

Why, when you're little, you're not afraid of public speaking?
When I was little, I was so out, I remember wanting to be in front of the class and talk to the kindergarten, I remember that the teacher let us sit in front of the class and read. I was not nervous at all about this. Also, I liked to entertain the crowds. It took until the 6th grade, I started be shy and I like most people hate public speaking now. Is there a psychological reason why he was so brave to face people and speak when I was little and now I think ID rather die? I mean nothing traumatic has actually happened to me. Is it normal do not care when you're small and then grow to be afraid of something like that?
Because during this stage, no do not stain dirt, negatives, imperfections in our hearts. It (the heart) is clear or transparent glass. No fear. N shy. On opening. This helps a lot, I think.
Fearless Public Speaking Workshop and Video