The phrase "at ease" means that the people thought that they lived in peace and security. Alternate translation: "I am very angry with the nations that enjoy peace and security" (See: [[rc://en/ta/man/jit/figs-idiom]])
"the nations that are at ease made the disaster worse." This means that although Yahweh used these nations to punish Jerusalem, they did more harm to Jerusalem than what Yahweh had intended for them to do. (See: [[rc://en/ta/man/jit/figs-explicit]])