Which detail from Jim Murphy’s The Great Fire best supports this thesis?

"An exhausted Chamberlin came to the Randolph Street Bridge and discovered 'a torrent of humanity pouring over the bridge. The Madison street bridge had long before become impassable,'"
"Soon, he, too, was filled with a new determination; Storey borrowed money from friends, dug out some old type from his barn, and had the Times publishing again on October 18."
"You can imagine the reunion that followed and how happy I was to learn that Mother, Willy, Robert, Jr., and Charlotte had all escaped the fire and were now staying with a generous family who had opened their door to them."
"After describing at great length how solid and fireproof the Tribune Building was, Mackintosh paused and, with a sad sigh, he concluded, 'That is, it was fireproof up to the date of its destruction.'"