This means that the only problem with relying on the single bridge was that it was blown prematurely. The Genie officer who would have been busy building temporary bridges was instead tasked with blowing the single bridge. The strategy -as demonstrated by the task assigned to Monfort- was that it was a more important to cutoff any enemy pursuit than to make retreat easier.
There were no temp bridges because N. didn't want them and, if the bridge had been blown at the right time, it would have been hailed as another of N.'s great strategic moves. Other observers are going to be biased by the results of the bridge explosion and ask the question of why more temp bridges weren't built. If everything had gone to N.'s plan, they would be marveling at his genius.
See the GA bulletin of Oct 20, which describes the French Army leaving Leipzig victorious right up until the bridge incident, placing the entire blame of N.'s defeat at Leipzig on the Genie Colonel.