The state attacked the Nation of Islam as a cult, not as Islam. [causal]
The Nation of Islam's reclamation of black dignity by way of emphasizing the importance of family, racial pride, and community empowerment threatened the state. Yet the state, latching on to the narrow view that Muslims were an immigrant bloc from the Middle East, largely viewed the Nation of Islam and its leaders as religious charlatans. Thus, attacks on the Nation of Islam were largely racial and political; when it was attacked on religious grounds, it was attacked more as a cult than as Islam.
XREF: Connects to patterns of how states misclassify religious movements they find threatening, reducing them to illegitimate categories like 'cult'.
Khaled A. Beydoun, American Islamophobia_ Unde…, loc. 439