Passengers want to get to their destination as fast as possible – If the train going past C is faster than waiting for a train going directly to A, they’ll board it. Even if it isn’t particular “real life” realistic.
Edit: You’re using the wrong kind of link for an image post. But here’s the URL for the image for anyone else.
Actually it is the same line, ABCBA ( A straight line and not loop). Cart goes to A then B then C, and then reverses to B to A So when the cart is going from B to A, time is shorter. But passengers are willing to go to C for no reason, to reach A which is closer.
As a consequence, C is flooded with waiting passengers,