Looks about the same condition as a brick chimney I seen at a customer's home a few years ago that took a direct hit.
I heard once sap turning to steam was what caused the tree bark to explode. But you see something like that and you have to ask what other physical phenomina is occurring. There would be very little internal moisture in bricks or a structure like that. Really only the moisture from the rain on the outside. Something must also be happening on a molecular level. Like seeing sand changed into glass from a lightning strike or a downed power line. Never fails to amaze that is for sure.