Final answer:
Boys' train culture shifted their fascination from steam locomotives to electric trains and automobiles with the advent of new technologies and cultural influences in transportation.
Step-by-step explanation:
The dreams of boys' train culture increasingly shifted from the steam locomotive to electric trains and automobiles, marking a transition in transportation technology and the fascination that comes with it. By the early 20th century, advances in electricity and internal combustion engines paved the way for these new technologies to capture the imagination and interests previously held by steam trains. Moreover, cultural shifts promoted other forms of transportation, such as cars which provided individual flexibility, and electric streetcars which were seen as modern and sophisticated forms of urban transit.