Adding to this, Fortos adds valuable context on the election of Khamenei:

Usually, the leader of Iran can recommend a successor to the Assembly of Experts, and the members take it into consideration when voting.

Imam Khomeini recommended Martyr Imam Khamenei.

However, Imam Khamenei did not have a recommendation, and left the decision completely up to the Assembly of Experts; who independently from all institutions, parties, and figured; chose and voted for Seyyed Mojtaba Khamenei.

So it’s not like his son succeeded him as in a monarchy system. He was elected through a complex and thorough voting system.

@FotrosResistancee