Henry Kissinger has believed that carrot and stick should be used at the same time to be effective.
As congress passed sanctions against Iran’s conservative individuals and organization, the system must facilitate political, economic and cultural investments in Iran in a tangible way, in order to simultaneously weaken the position of hardliners and strengthen the bargaining power of Rouhani against domestic conservatives over the subjects of human rights and regional issues. Although, John Kerry has sought to transfer a false message to Iran about the sanctions in order to back the stance of the Iranian right wing.
Also nowadays security is a strategic commodity. Thus, there is no blame on Iranian intelligence for letting terrorists to implement their plan in order to have the upper hand over the Rouhani administration, though the intelligence were informed. Simply, it is a common practice in the politics. However, since Tehran is a strategic position, the system will try to fill this security vacuum. In this regard, based on classified information, Tehran city council is next target of terrorists, which should not be considered a winner card for conservatives anymore!
Certainly the system intends to keep current role of Iran in the Middle East. Terrorism and Saudi Arabia are two major troubles of the region. The first one targets security and the second, is a threat to democratic movements and political independence of countries. Iran is the only power that efficiently confronts them.