crisis opportunist

A person or business-establishment that "moves in for the kill" whenever others are in a tight spot, hoping to "score big" due to the victims-of-circumstance's feelings of helplessness and desperation.

Some high-school guys with raging hormones purposely cram and toil to "exceptionally learn" math, English, history, science, etc, so that they can then extract sexual favors from less-competent girls who need help with their homework --- what shameless crisis opportunists!