The question "why did the 9" seems to be an incomplete query possibly referring to "why did the 9/11 attacks happen." The 9/11 terrorist attacks on September 11, 2001, were carried out by 19 Al Qaeda terrorists who hijacked four commercial planes in the United States to inflict massive destruction and loss of life. The attacks targeted the Twin Towers of the World Trade Center in New York City, the Pentagon near Washington, D.C., and a fourth plane crashed in Pennsylvania after passengers intervened. This act of terrorism was motivated by al Qaeda's goals against the U.S., leading to nearly 3,000 deaths, a global impact, and subsequent U.S. actions such as the War on Terror and invasions of Afghanistan and Iraq. The attacks aimed to cause economic damage, instill fear, and challenge U.S. influence globally.
If further details about specific motivations or consequences are needed, or clarification on a different aspect of "why did the 9" is desired, additional questions can be provided.