It's the same scenario as Mad King (Vis dev).
He also left, deleting his Patreon and all his social media accounts too.
If the dev leaves the Patreon open, it does leave possibility that he may come back in the future (it can lead to a bit of scrutiny that dev may be milking, though in the end, up to Patrons to decide whether to continue support or not I suppose).
But if the dev cut ties for good like in this case here, it seems something happened irl which led them to that decision.
Hope they are okay, but yeah.
It's a shame.
Cause I quite liked both games (with this one, I liked how Professor Historian used a setting that really isn't used in other games).