This is not uncommon. There have been dozens of reports of people who just dig because they find it peaceful and comforting.
It’s probably beneficial behavioral survival mechanism. As humans we like to think we’re immune to natural or inherited instincts, but that’s probably not true. If we slow down and listen we would probably hear a lot more of them.
Having a member of your tribe who likes to spend their free time digging tunnels turns out to be a beneficial survival trait in a lot of unexpected but lethal eventualities.
Mentioned in passing in a recent Practical Engineering video on tunnels. https://youtu.be/Ssw5bdx1HKw?si=DfOLWszK4erDPe3n
Got The Wind-Up Bird Chronicle vibes from the story.
(2015)
The follow-up article is lovely too: https://macleans.ca/news/canada/passing-the-headlamp-the-tor...
And this one later in 2015 that speaks to his use of the fundraiser money: https://www.thestar.com/news/insight/york-u-s-mystery-tunnel...