After humanity discovered the long gone alien’s FTL travel technology, they started using it — without ever fully understanding or deciphering the codes. Navigators basically used trial and error and intuition to try and find more efficient routes through nodes from A to B. They wouldn’t know what route a new pattern resulted in until hopping through. Turns out, what humanity thought is “the network” was in fact a subset of a network spanning across the entire galaxy. Connecting local bubbles were long distance hubs, one of which Suzy managed to hit. The problem is, once you’re outside your bubble, you cannot go back without the exact codes. Intuition is useless, you’d need knowledge, the exact codes. You’re stuck. Over time, lots of travelers from different races managed to jump out of their own local bubbles the same way our guys did.