The word "They" refers to the people who were hungry that Yahweh had settled in the land. This sentence describes how they were before Yahweh settled them in the land.
This can be stated in active form. AT: "Their leaders diminished their number and brought them low" (See: [[rc://en/ta/man/translate/figs-activepassive]])
Here David speaks of Yahweh showing contempt for the leaders as if contempt were a liquid he poured out on them. AT: "shows contempt for" (See: [[rc://en/ta/man/translate/figs-metaphor]])
"the nobles." This refers to the leaders who oppressed the people. AT: "the leaders who oppressed them" (See: [[rc://en/ta/man/translate/figs-explicit]])