The FLN achieved mass movement status by absorbing political rivals. [causal]
Thus, by this time, the absorption or neutralisation of its principal political rivals, M.N.A., P.C.A. and U.D.M.A., had transformed the F.L.N. into a “mass movement” in the truest sense of the word.
Horne, Alistair, A Savage War of Peace- Alge…, loc. 440