The extraordinary collapse of the Assad regime over the weekend is a historic victory for the Syrian people, who for over a half-century have suffered under the Assad family’s brutal authoritarian rule. It will undoubtedly pose challenges and create opportunities for the United States and its allies in the Middle East and beyond.

Understanding what led to the regime’s collapse will be key to putting the country back together and achieving the elusive goals of successive U.S. administrations: cutting off Iran’s ability to project power across Syria to Lebanon and Israel, and bringing American forces home from their long deployments in Syria.

At the heart of President Bashar al-Assad’s fall was his government’s rigidity and unwillingness to keep up with a rapidly changing Syrian society. After he came to power in 2000 following the death of his father, Hafez al-Assad, Mr. al-Assad promised to change one of the world’s most brutal dictatorships. He urged Syrians to respect one another’s views and pledged domestic reforms to accommodate large waves of young Syrians. Encouraged by these pledges, presidents, kings and queens courted Mr. al-Assad and his glamorous wife, Asma, with the goal of achieving Arab-Israeli peace and breaking Syria’s longstanding alliance with Iran.

Meanwhile, in Syria, not much changed. While the regime tolerated some dissent in the first year of Mr. al-Assad’s rule, what came after was an ambiguous authoritarian Potemkin reform process to pave the way for trade and other activities in Syria, but which had no legal foundation. Syrians were forced to pay bribes to regime officials, making it one of the most corrupt business environments in the world. The police state continued to arrest opponents, and repression and torture continued for the remainder of Mr. al-Assad’s chaotic rule, while the economy plummeted, sending a vast majority of the population into poverty.

For those of us who engaged with the al-Assads, it was a puzzling experience. In meetings they would promise reforms in Syria’s domestic and international policies while asking for patience to carry out changes. It was a seemingly reasonable request, given the daunting task of transforming a centrally planned former Soviet satellite state.

But shortly thereafter, something contradictory would occur that would call the al-Assads’ promises into question. In the spring of 2010, American negotiators thought they had achieved Mr. al-Assad’s buy-in on a peace agreement with Israel that would return the Golan Heights to Syria’s control in return in return for Mr. al-Assad distancing Syria from Iran and cutting its supply lines to Hezbollah in Lebanon. Instead, satellite images taken around that time emerged showing that the Syrian Army was possibly training Hezbollah activists on how to use Scud missiles — strategic weapons that can carry conventional and chemical payloads with the potential to destroy large parts of Israeli cities — at a Syrian base.