They were released in trickles after the Gulf War. Coincidence? Why did they finally decide to let them go?
It originally ties into the Iran-Contra scandal, actually.
*The first 100 missiles arrived in Iran on August, 30, 1985, and the remaining 400 on September 14, 1985. This arms transfer helped lead to the release of one U.S. hostage - Reverend Benjamin Weir - on September 14, but ity did not lead to the much larger release of U.S. hostages that the White House officials expected. In fact, Iran established a pattern that it was to repeat throughout 1986, when the U.S. shipped arms directly to Iran. Iran released one hostage but kept the others to retain its leverage over the United States…
…On each occasion, the pro-Iranian groups in Lebanon carried about only one-third to one-half the releases the U.S. expected. Further, Iran seems to have encouraged such groups to take new hostages in compensation. By the time the covert U.S. arms deals became public in early November 1986, pro-Iranian groups had as many U.S. hostages as they did before the arms deal.*
From The Lessons of Modern War, vol. II:The Iran-Iraq War by Anthony Cordesman and Abraham Wagner ( 1990, Westview Press, Inc. ).
Ultimately the release of hostages was trickled out in Lebanon in part because Syria and Iran stood to gain prestige by playing up their efforts to secure release, in part because they had ceased to be as useful of bargaining chips, and in part because the situation on the ground changed as the Lebanese Civil War officially ground to a halt in 1991 around the same time as the Gulf War.
- Tamerlane