> Religious infighting with 2 fundamentalist sects that somehow boiled down to some people digging a tunnel connecting 2 buildings because of... reasons?

The very short version is that both groups claim ownership of that building, and one of them wants to expand it significantly. Neither group is allowed to modify the building because of a court order, so the one that wants to modify it did it surreptitiously in an attempt to create facts on the ground that would modify the status quo.

(Obviously none of this is sensible, but the actual reasons are pretty quotidian.)