The decrease in demand and increase of supply is described perfectly in our Economics textbook “Supply Increase; Demand Decrease. What effect will a supply increase and a demand decrease for some good (for example, apples) have on equilibrium price? Both changes decrease price, so the net result is a price drop greater than that resulting from either change alone (57)." The first event was Iraq’s return to normality and stability, which allowed for Iraq to drastically increase its oil production. And the second Macroeconomic event is that the Asian countries with leading GDPs were engrossed in a financial crisis causing Asia’s demand for oil to decrease significantly.
Notice the chart between 1991 and 1997 is the gulf war and how low the oil production is, and notices the spike in Iraq’s oil production after the war. The market would have had its equilibrium at around $34 a barrel just before Iraq nearly doubled its daily output of oil barrels per day from 750,000 to 1.5 million barrels a day, from which Iraq’s supply to the market only increased.