well, one explanation may very well be that they are trying to weaponize cyanide
cyanide is cheap and relatively easy to produce so it makes sense(in a very morbid way)to try that

PROFESSOR ALASTAIR HAY, ENVIRONMENTAL TOXICOLOGY, UNIVERSITY OF LEEDS:
The science seems to fit together. And in 1979 it was probably original, pioneering research. It doesn't seem to me it has been invented. Why go into this level of detail? Why run the risk of getting it wrong and being exposed? The chemical that was being made is one called Para Cyano Nitrobenzene. There is very little known about it and the description he gives of the effect it would have on individuals do fit so my feeling is it is probably correct.