An idiom carries a settled figurative meaning that cannot be worked out from the separate words, so the literal picture it paints has to be set aside. The image here is of someone deliberately stirring up or exploiting muddy, agitated water because fish are easier to catch when they cannot see clearly.

Carried into human affairs, the expression describes a person who takes advantage of a quarrel, a crisis or any state of confusion in order to gain something for himself. The gain is private and the disorder is what makes it possible, and that combination is what the correct choice states.

The choice about catching fish is the literal reading of the words and is exactly what an idiom does not mean. Merely starting work in an unsettled atmosphere describes a circumstance and names no benefit to anyone. Enjoying difficulty points to courage or relish for a challenge, which is a quality of character and carries none of the selfish advantage the idiom conveys.

to make personal profit out of a disturbance option is correct.