Wiegley as maintainer was discussed in the gnu emacs dev mailing list for the past couple of months, hundreds of messages.
John Wiegley is the author of eshell, among others, and he lives in emacs. 〔➤ Emacs: M-x eshell〕
Here's a couple of video interviews of John.
John is a extreme emacs enthusiast, and his primary platform is Mac with strong desire to make emacs better on Mac too out of the box, and he is a very capable programer, and also a sociable person. I think John will bring a lot good things to emacs. Thanks John.