The term translated as marveled
can indicate a positive response (admiration; see Mark 5:20) or a negative response (being horrified). Clearly, the negative sense is intended here. The image of such a prostitute taking advantage of earthlings—particularly God’s people—to the point of drunkenness through their blood is deeply troubling to John.
6 And I saw the woman, drunk with the blood of the saints, the blood of the martyrs of Jesus.When I saw her, I marveled greatly.