Notre Dame Cathedral would have burned to the ground in a “chain-reaction collapse” had firefighters not moved as rapidly as they did to battle the blaze racing through the beloved landmark building, a French government official said Wednesday, as nearly $1 billion in pledges poured in toward the rebuilding effort. Firefighters acted aggressively to protect wooden supports in the twin medieval bell towers from the flames, averting a bigger catastrophe, said José Vaz de Matos, a fire expert with France’s Culture Ministry. “If the fire reached this wooden structure, the bell tower would have been lost,” de Matos said at a news conference. “From the moment we lose the war of the bell towers, we lose the cathedral, because it’s a chain-reaction collapse.” Monday’s fire destroyed most of the lead roof of the 950-year-old architectural treasure and caused its spire, which was added in the 19th century, to collapse. NBC 4 New York on Twitter: 4.nbcny.com/kAuuwUN NBC 4 New York o...