Because there is SO much fine detail in this photo your eye gets lost. The eye loses the trolly which is your focus. If you cut out the whole right half of the image and some of the bottom you get a better sense of movement from the trolly.
On a side note while I was playing with this image in PS I noticed something. If you Desaturate it, do color Varations, then bump the Contrast this photo makes a great vintage looking photo. In normal color it's quite obvious that it's a train set, but the eye can almost be fooled by taking all the colors out and just having the one overlay color. If the plants were more to scale you could travel in time.