The early Railway stories were based on real railway incidents, and the characters were based on real models of locomotive (Thomas is LB&SCR E2 class). The technical details provided a lot of the stories’ appeal, at least to some children. The stories took ideas from the realm of science and engineering and made them entertaining by weaving stories about them.
See where I’m going with this? The Railway stories have a lot in common with hard science fiction. Especially for modern children, for whom the technology described is outside of their lived experience and therefore as imaginary as an interplanetary rocket.