Sleeping represents dying. Alternate translation: "Azariah died as his ancestors had" or "like his ancestors, Azariah died" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-euphemism]])
The phrase "in his place" is a metaphor meaning "instead of him." Alternate translation: "became king instead of Azariah" (See: [[rc://en/ta/man/translate/figs-metaphor]])