If the comet hit a large body of water, it could have created a tidal wave. Perhaps the source of Noah’s flood?
How would that start fires?
The hypothesis is multiple fragments impacted the glaciers across North America and northern Europe. Instantly melting a large portion of the ice resulting in massive global flooding. This fits a large number of the flood myths across the globe.
Younger Dryas impact theory.
https://en.wikipedia.org/wiki/Younger_Dryas_impact_hypothesis