Second, the fire didn't melt the columns, it primarily weakened them (unevenly) to the point that collapse was not only possible but inevitable. Considering that you like YouTube videos, this one actually does a fairly good job of explaining the affect of the fires in layman's terms.
It is also only about 4 minutes long, so shouldn't be too much of an inconvenience to watch. The video you want us to watch is an hour and 19 minutes. I will watch it later, but don't have the time right now.