Being an introvert and being afraid of public speaking are 2 different things.
Introverts find it hard to engage in small talk, introverts think before they speak, introverts do not enjoy loud crowds, let alone trying to make yourself heard in them.
But, introverts can be great public speakers. On stage, there is no small talk, but the real substance of your presentation. People are quiet and listening to you. The perfect spot for an introvert to shine.