Many introverts are quite good at talking to crowds. Speaking as an lifelong introvert myself, crowds are easy. It's individuals that can be difficult.

"Introverted" and "shy" are not the same thing.

Many entertainers are introverts--the actor who vanishes back to his trailer the second the cameras stop rolling is almost a stereotype. Introverted politicians are less common, but they exist as well. Richard Nixon and Jimmy Carter are both famously introverted.

The distinction between introvert and extrovert has little to do with willingness to appear in the public eye. It's about where you find your energy: The introvert is drained by dealing with people and recharges in private, while the extrovert finds social interaction invigorating and solitude draining.