Out of curiosity I actually looked up the details on this scene a while back. There is some actual real model of circuit breaker this scene was based on; I think someone dug up the model number, but I can't remember it now.

It turns out a lot of high-power circuit breakers need the energy from a clockwork mechanism in order to open in the event of a fault. So the thing where you have to pump the handle is actually to charge a clockwork mechanism to ensure there's enough mechanical energy to open in the event of a fault - AIUI. Presumably, the breaker is designed with safety in mind and won't let you push-to-close until you've done this.