Why did hurricane Matthew happen?

Like many Atlantic hurricanes, Hurricane Matthew began as an area of disorganized thunderstorms, called a tropical disturbance, that moved over the Atlantic Ocean from eastern Africa. The National Hurricane Center labeled it Invest 97L as it began monitoring the system. Following the trade winds in the tropics, 97L moved west across the Atlantic, slowly becoming stronger and more organized as it fed on the moisture from the warm water. Just east of the Caribbean Sea 97L, which was already producing strong winds, became organized enough to be called a tropical storm, and was named Matthew. A day later, Matthew became a hurricane and, fueled by moisture from the warm Caribbean, entered a period of explosive strengthening and briefly reached peak intensity as a category 5 hurricane.

Steered by a general clockwise flow of air that covers most of the Atlantic, Matthew turned north, maintaining category 4 strength. After a few days on this track, Matthew slammed into the vulnerable nation of Haiti, and then into the eastern tip of Cuba later that day. Matthew continued on its northward track, moving across the Bahamas as a category 4 and skimming up the coast of Florida, though without making landfall, as it began to gradually weaken. The storm continued up the east Coast and finally made landfall in North Carolina.

Haiti suffered the worst effects. It is, an impoverished nation, is ill-prepared for any hurricane, let alone a category 4, and is still recovering from a major earthquake in 2010. The poorly-built homes stood little chances against the 145 mph winds and deforestation has left much of the nation prone to flooding and landslides. The unusual path that Matthew took, moving parallel to the U.S. coast with the eye just offshore, ensured that the storm impacted a very large section of the U.S. with wind, rain, and storm surge. Matthew dropped and unexpected amount of rain over the Carolina and Virginia, causing record flooding there as well.