I know why actors are notoriously shy and mean and why learned people can't bear to be on a stage in front of people. There are two world views here, and two stereotypical people types.
One is a view of the world at large being incomprehensible and scary as hell, this person type is timid and an desperate for control of the events around them, they no nothing of themselves and are afraid to look.
The second view is that the world is a playground and the chaos is fun, this person type is daring and laid back when it comes to life issues, they know themselves and self reflection is term they will understand well.
Now acting/singing/performing is a controlled environment and as such the rules are easy to learn and control, they can be achieved by a craving personality. Life however is vast and uncontrollable, random acts happen and the rules are not stated anywhere. Life is inaccessible to a craving perosnality but is available to an open and free mind.
So you can see that the person needing control is lost in the world, but can excell in a studio or on a stage where reapeated steps/lines can be controlled. They are afraid of life and because of this will most likely end up an indecent and immoral being.
Now the person who is at one with the chaos of the world is absolutely lost in a controlled environment because they are so aware of the random possibilities that can happen, they feel that everyone else is aware of them too. It is because of this, a simple task of standing in front of an audience and speaking becomes an almighty problem for them. They don't realise everyone else is using a simple trick to block all of the possibilities and ignoring the reality. This type of person with this world view is going to be far more moral and just than the other.
what does this all mean? Beware of people who are naturally confident in small controllable situations such as public speaking, acting, or performing as they are terribly afraid of the world and of people. They do not understand them and are too afraid to ask.
On the other hand seek out people who cannot act or sing in front of people because while they do not like rules and controls, they are confident in life and will do the right thing when the crunch happens.
Because they are not told what to do in life, because the rules are not stated they cannot find rules for themselves.