This is a polite way of saying that he died. Alternate translation: "Ahaz died" (See: [[rc://en/ta/man/jit/figs-metaphor]] and [[rc://en/ta/man/jit/figs-euphemism]])
The phrase "in his place" is a metaphor meaning "instead of him." Alternate translation: "became king instead of Ahaz" (See: [[rc://en/ta/man/jit/figs-metaphor]])