I believe the steel in the house was very effective in grounding out the lightning but it didn't happen until it had blown a hole in the roof sheathing to get to it. By then it had sought alternative paths, probably through the power line.
I have said this before. I took a direct hit on my weather station mast last summer with minimal damage but I did have an air terminal on top of it with a #2 going as straight to ground as possible.
