رُؤُوسًا جُهَّالًا refers to ignorant leaders; جُهَّال is a plural of “ignorant.” فَسُئِلُوا means “then they were asked,” and فَأَفْتَوْا means “they issued rulings”; فَـ links the sequence.
فَضَلُّوا وَأَضَلُّوا separates going astray oneself from leading others astray. The second verb adds the sense of causing others to err.
A responsible response is: “I do not know enough to answer this; consult a qualified scholar.” Confidence of tone is not proof of expertise.