Hosea uses the term "Ephraim" to refer to the entire northern kingdom, although it was also the name of one of the ten tribes. Hosea seems to be speaking of a long-past time, when the northern kingdom was strong and honored, unlike at the present time. (See: [[rc://en/ta/man/jit/figs-synecdoche]])
It is understood that people were trembling because they were afraid of Ephraim. This can be stated clearly. Alternate translation: "there was trembling among the people" or "people trembled in fear" (See: [[rc://en/ta/man/jit/figs-explicit])
When the people of Ephraim began worshiping Baal, they grew weak, and their enemies defeated them. Here "died" refers to the nation growing weak. (See: [[rc://en/ta/man/jit/figs-metaphor]])