Notice how Paul says they sacrificed "to demons (idols) and not to God" - the demons were not God, and as there is only one God, it follows that demons have no real power at all, they are not gods. The point is really driven home in 1 Cor.8:4:-
Tazama jinsi Paulo anavyosema walitoa sadaka "kwa mashetani (sanamu) si kwa Mungu" - Mashetani hawakuwa Mungu, kwa kuwa yupo Mungu mmoja, kinachofuata ni kwamba mashetani hawana uwezo wowote wa kweli kabisa, Si Miungu. Sababu hasa inatoka katika 1Kor. 8:4:-