While the Bahraini crown prince did indeed travel to Saudi Arabia, it is not certain Bahrain's prime minister traveled to Iran. The purpose of the purported visit was apparently to seek Iranian assistance for Manama’s attempts to pacify the Bahraini Shiites. Whether or not Bahrain sent a delegation to Tehran, the key fact remains that Bahrain is geopolitically caught between the Saudis and the Iranians.
Bahrain, an island nation, is linked via a causeway to Saudi Arabia and through its Sunni al-Khalifa rulers. At the same time, some 70% of the country's Shiite population, whose political principals are Islamist, pulls the tiny Arab country into the orbit of Iran. In fact, the country only came under Sunni Arab rule toward the end of the 18th century. Prior to that Bahrain was under various periods of Persian and Shia control for many centuries.
The unrest in the region, especially in Bahrain, provides the Iranians with a historic opportunity to wrest Bahrain from Sunni Arab control and gain a foothold on the other side of the Persian Gulf. The Iranians are not about to squander this opportunity. Tehran has long been engaged in covert intelligence operations in Bahrain.
From Iran’s point of view, the current situation where the al-Khalifas are in negotiations with the largely Shiite opposition should at the very least result in a compromise offering significant concessions to the majority community. The al-Khalifas may have to give up some powers to parliament. Such an outcome is unpalatable for Saudi Arabia and the United States.
More problematic is that Riyadh and Washington do not have many good options to prevent the empowerment of the Bahraini Shia and Tehran. The Saudis have no qualms about opposing the demand for democracy but they have very little room to maneuver. The Americans have far more room to maneuver but cannot oppose calls for the monarchy to engage in democratic political reforms.
In the end, public agitation for democracy in the Arab world is a potentially powerful tool in Tehran’s hands. First, it allows the Iranians to turn an American weapon against Washington. Second, it could do away with structures that have thus far blocked Iran. Third, it empowers the Islamic republic’s Arab Shiite allies. Regional geopolitical conditions have never been this favorable for Iran since the 1979 foundation of the Islamic republic.