Catastrophic bridge failures occur due to a combination of factors. The article explains some of these factors and how they lead to bridge collapses. One major cause is design flaws and poor construction techniques, leading to weak and unstable structures. Another factor is inadequate maintenance and inspections, which can result in structural deterioration and weakens the bridge over time. Lastly, natural disasters like earthquakes, floods, and hurricanes can also contribute to bridge failures by exerting excessive forces on the structure. Understanding these causes is crucial to preventing future disasters.