Creative Speculation

Let's assume he meant "secretly demolish the building and then collect insurance".

These guys never seem to want to talk about the actual context in which they base this particular piece of nonsense - i.e. a discussion he had with FDNY officials.

If we accept the premise as true, the way this shakes out is that Silverstein instructed to the FDNY to do it, the firefighters somehow were prepared to do so in a burning building on short notice, AND they kept their mouths shut about their own complicity in an incident which claimed many of their own lives.