It should be noted that this article is from 2017.
He’s a passionate cartographer, and has been posting about maps since 2010, 2017 being his rise to popularity not withstanding.
(This misconception comes from a 2017 Verge piece on "Google Maps' Moat" that misstated that he was.)
Source/Disclosure: I'm a close friend.
Perhaps I used the word “cartographer” incorrectly. I apologize, my native language is German so English is not always 100% forthcoming to me.
I don't think that there is an English word for someone who likes maps. The best thing to say is what you already said: that they are "passionate about maps".