For decades, Iran's Supreme Leader exercised nearly complete power. However, now that Ayatollah Ali Khamenei has been slain, his son, Mojtaba Khamenei, is unlikely to have the same 'untouchable' reputation. He'll have to share more power than his father did.
Over time, leadership in Iran has discreetly shifted away from a single person and toward a "collective" or network of influential groups. These include the Islamic Revolutionary Guard Corps, which has gained tremendous power due to its control over military force; the intelligence-security apparatus, which handles spying and internal security; and the financial elites.

The Iranian system, known as Velayat-e Faqih (Guardianship of Islamic Jurists), has gradually evolved. The Iran conflict has been going on for 12 days, and it has simply escalated the situation.
There is insufficient time for a single person to make every decision. In a crisis, the organizations who have actual control over the guns and information, such as the military, naturally take the lead. This results in the government functioning more like a'security bureaucracy' than a religious monarchy.
A network of strong insiders is currently making decisions to secure the regime's survival during the war.According to Babak Vahdad, a researcher and analyst on Iranian dynamics and Shiite Islam, the Islamic Republic has evolved towards a system where power is increasingly exercised through interlocking networks, despite the supreme leader remaining the apex of legitimacy.According to Vahdad, Khamenei's death during a war accelerates the process.In practice, this almost certainly increases the relative weight of actors such as the IRGC, the intelligence-security apparatus, and key regime coordinating bodies, not because they formally replace the supreme leader's office, but because crisis management favors institutions that control force, information, and operational continuity," Vahad added.

In an interview with Axios, Trump stated that Mojtaba Khamenei, the 56-year-old son of late Iranian supreme leader Ali Khamenei, succeeding his father as the new leader of the Islamic republic is "unacceptable" and that he prefers someone who will "bring harmony and peace to Iran."
Trump stated that appointing a leader who would continue Khamenei's views would require the US to go to war "in five years".
When asked who may succeed Khamenei, Trump told reporters at the White House on Tuesday, "Most of the people we had in mind are dead."Vahdad claimed that Trump's criticism of Mojtaba Khamenei boosted popularity for the newly elected Supreme Leader. "The IRGC is pushing his standing especially after Trump's latest statements against him, which definitely increased his support even beyond IRGC network," Vahdad pointed out.
Iran's Assembly of Experts has elected Mojtaba Khamenei as its new leader. Despite being a mid-level cleric, he is thought to wield enormous authority over Iran's security forces and large enterprises originally affiliated with his father.
Prior to the announcement, Israel threatened to strike whoever was chosen. It provided no follow-up.