Like Russia, China, and North Korea, Iran sees a weak American President and Administration and feels it can get away with piracy. Democratic Presidents from Truman onward have been seen as weak. Truman and Marshall had previously sold out the Nationalist government of China, allowing the Communists to take over. The North Koreans reasonably thought they could conquer the South with little American opposition. Similarly, when Kennedy failed to support the Cuban exile invasion at the Bay of Pigs, the Soviets believed the U.S. would do nothing if they placed missiles in Cuba.
Yep weak mean lead to hard times.