How can I help a co-worker who has a stutter?

How can I help a co-worker who has a stutter? I hope this sort of post is okay here. If not, please let me know and I will remove it. I facilitate a team at work, and one of the members of the team has a stutter. I didn't realize it for a long time because he would rarely speak during team meetings. His contributions were always through the chat (we all work remotely through Zoom). I just assumed he was shy, something I deal with a lot myself and have empathy for. It wasn't until I set up individual meetings with each member of the team that I noticed his stutter, because the type of meeting necessitated speaking rather than typing. In the team meetings since, it feels like his silence is so much more pronounced. Maybe it's just in my head because I'm aware that it might be due to more than just shyness. He still communicates through chat, but there have been a couple of times other members of the team have asked him for his thoughts and he just remained silent until they moved on. This guy is brilliant. I'm thrilled to have him on my team, and I want to hear more from him. His chat messages are fine, but sometimes I need further explanation to understand the point he is making, which forces him to speak. I have enough patience to wait for him to finish without rushing him, but I recall hearing or reading once that sometimes a stutter will get worse when the person knows people are waiting for them to speak or finish what they are saying. I certainly don't want to make it harder for him if that's the case. What can I do to reduce stress or pressure or whatever that might exacerbate his stutter? How should I behave? Any input and suggestions you have would be greatly appreciated. I understand this probably isn't a one-size-fits-all sort of issue, but any guidance is better than none, I think. Thanks, all.