JayUtah
Penultimate Amazing
There are any number of ways that weekend 'renovation-al work' could have been orchestrated. The important part would be to make sure that fresh drywall was in place before the next work day.
Such as ... ?
Any documentary or eyewitness testimony to confirm that any of that purported activity did happen?
But, I can see how it could be part of something much bigger which could take out major columns.
So the nanothermite is no longer the magical element. The magical element is now something else, which you haven't yet decided upon.
My best guess is that thermite would be used to initiate a major structural failure...
Again, noiselessly. You still haven't described what new magical substance can cut structural steel without leaving a trace.
Appeals to magic are not resolved simply by appealing to more esoteric magic.