Although it sounds exaggerated that a single subway malfunction could cause the entire network to grind to a halt, if the affected train had stopped at a critical point, and if at that moment this critical point could indeed impact the whole subway network...
Like a row of dominoes, toppling one could lead to the fall of all. A malfunction in one train would inevitably affect the whole line, and the temporary stoppage would involve other intersecting routes. Under this chain reaction, impacting the entire Tokyo subway network, although it sounds exaggerated, was actually not impossible.
For one of the largest cities in the world like Tokyo, a subway halt was a serious matter, so naturally Tokyo subway operators sought to resolve the issue immediately.
But unfortunately, just as a building can collapse in an instant while clearing the rubble takes a long time, restoring the entire subway network was not something that could be done right away.
