A clever and meaningful answer
2-The second reason is the necessity of knowing the Imam of each era:
"It is a sign of faith"
Aban ibn Taghlib says: “I asked Imam Sadiq: Is a person faithful if he knows all Imams except for the Imam of his own era? The Imam said: “No.” I asked again: Is he considered as a Muslim?
The Imam answered: “Yes.”
The Source: Kamal al-Din and Tamam Al-Nimeh
The important lesson:
"Every Muslim is not considered as a faithful one"