The servant causing the people of the nations to be acceptable to Yahweh is spoken of as if the servant were a priest who sprinkles the blood of a sacrifice to make someone or something acceptable to Yahweh. (See: [[rc://en/ta/man/jit/figs-metaphor]])
The phrase "shut their mouths" is an idiom. Alternate translation: "kings will stop talking" or "kings will be silent" (See: [[rc://en/ta/man/jit/figs-idiom]])
This can be stated in active form. Alternate translation: "that which no one had told them" or "something no one had told them" (See: [[rc://en/ta/man/jit/figs-activepassive]])