Bet the smart kids in the class are squirming in their seats!

My take on it is a quick and intensely hot chimney fire. I see dark discoloration at the bottom flue section. Perhaps a creosote coating in that section flared. Looks like heat signatures, seen on the upper most section left side. Fast and hot meets cold and brittle resulting in thermal shock cracks.

Is this for a wood stove? Isn’t that a chimney connector sticking way too far into the bottom?

Thanks for the photo challenge!