Often in prophecy events that will happen in future are described as happening now or in the past. This emphasizes that the event will certainly happen. (See: [[rc://en/ta/man/translate/figs-pastforfuture]])
The words "laid waste" and "destroyed" mean the same thing and emphasize that the city was completely ruined. This can be stated in active form. Alternate translation: "Enemy armies will completely destroy Ar of Moab" (See: [[rc://en/ta/man/translate/figs-doublet]] and [[rc://en/ta/man/translate/figs-activepassive]])