Why are the Infallible Imams from Imam Hussein, not from his brother Imam Hassan (PBUT)?

Answer

In the name of Allah, this is ordained by Allah; only Allah knows the reason. Should you contemplate this meaning, you will understand what we have indicated. For instance, why does Allah create you as a male from someone not otherwise? Why were you born in a certain era not before or later? Why was the Messenger of Allah the son of Abdullah, not the son of other uncles? Why was he from the descendants of Ismael not from Isaac? The suspicion gets wider, if you contemplate the obligation of praying at certain timings and not others and having a certain number of rakaat according to certain contexts. Why is the Quran in this amount? Why is the way of writing the letters of the words in the common shape not otherwise? Brother, we have to submit to Allah and his ordained commandments. It is not allowed to ask for the reasons why Allah does such things. Allah says: “He [Allah] is not asked for what He does. It is they who are asked for what they do.” Allah knows best.