Two replicas could be built. One could be packed with concealed nano-thermite to be detonated at the time the originals collapsed after impact. Then the results could be compared.
If the results were the buildings never falling and only falling like the originals if thermite was used, and if then an investigation found key world players involved. How would the events play out and would it lead to negative outcomes or positive outcomes overall.
Regardless of the outcome of this test, there will still be conspiracy theorists that will claim that the test preformed was somehow initially biased. Henceforth, additional testing will be rendered rather ineffective.