After three days of denial, it was a stunning about-face. On Jan. 11, Iran's Armed Forces General Staff admitted that one of its surface-to-air missile systems shot down Ukrainian Airlines Flight 752 due to human error. The full acknowledgment turned heads, yet there was a reason for Iran's reversal: The country has no desire to turn itself into a pariah but rather find a way to engage with the rest of the globe, limit the impact of U.S. sanctions and negotiate with the West. The frank admission goes to show that such strategic goals influence many of Iran's choices -- including its volte-face on the aviation disaster....