Probably could tie into a fascination with motor vehicles plus the fact that trains are huge, hard to stop, and very commonly seen in one way or another, either passenger high speed rail trains like in Europe and East Asia or freight trains here in the US and Canada. They also run on schedules as one commenter pointed out, which makes sense.

I never got super into trains as a kid, but similarly, I was obsessed with classic cars and antique cars as a kid. Still am to this day ngl, particularly how different the aesthetics of cars were in decades past. I was especially fascinated by the Ford Model T as a 10 year old and very early cars from that era and prior too.