They move forward
The first thing about the successful people who stuttered was... I would call it "they move forward."
They didn't think like, "OK, first I need to be fluent and then I'll move forward in my life." Nope. They started moving in spite of their stuttering.
They found a way to face their fears, their desire to hide the impediment, they're taking responsibility for their lives, and that's something we tend to avoid. They gave us an example how we can communicate excellently even stuttering.
Most people are afraid of public speaking. We all are at least a bit anxious about getting on stage and speaking in front of an audience. And that's exactly what they did at the conference. And they did it in a very engaging way. They were heroes, and they inspired us to be more active in our lives too.
The second thing about successful people who stuttered: they improved their speaking.