Reminds me of an estate sale I went to one time. Unassuming place, one of those tiny postwar homes about the same size as the one in this article - but with at least double or triple the density of this train layout in the basement. The owner must have been a very thin person, as the narrow winding paths around the basement in places measured no more than 8 inches, and the widest parts were only about 2 foot wide. In a 900 sq. foot basement, there was probably only about 50 sq foot of floor you could actually rest your feet on. The rest was all layout and boxes of trains and train accessories of all sorts - hundreds of tiny pots of specialty paint, miniature trees, "grass powder", special linkages and wheels, and more. Probably most of it got thrown away at the end of the sale.
People have hobbies, but I can't think of any circumstance in which I'd convert my basement into a deathtrap. There was less room than those hoarder houses you see on TV (but much more organized). It was genuinely concerning that they even decided to hold a sale there open to the public.
Truly one of the more bizarre things I've seen. Also, the upstairs? Mostly normal - you wouldn't even know the guy liked trains.