It is very likely that this event occurred before the conditions were introduced by Prophet Muhammad(saws). These conditions comprised of spiritual significance.
The conditions mentioned in hadith (Sahih Muslim) given by you in descending order are following:
01. The one who is most versed in reciting Allah's Book should act as Imam for the people,
02. then the one who has most knowledge regarding Sunnah,
03. then the earliest one to emigrate,
04. then the earliest one to embrace Islam.
In second hadith (Sunan an-Nasa'i) given by you
the one who is most entitled to lead the prayer is the one who has most knowledge of the Qur'an. I am confused.
Is it the one who recites Qur'an better or the one who has most knowledge of the Qur'an?Below is a hadith from Sahih al-Bukhari
Narrated `Amr bin Salama:
We were at a place which was a thoroughfare for the people, and the caravans used to pass by us and we would ask them, "What is wrong with the people? What is wrong with the people? Who is that man?. They would say, "That man claims that Allah has sent him (as an Apostle), that he has been divinely inspired, that Allah has revealed to him such-and-such." I used to memorize that (Divine) Talk, and feel as if it was inculcated in my chest (i.e. mind) And the 'Arabs (other than Quraish) delayed their conversion to Islam till the Conquest (of Mecca). They used to say." "Leave him (i.e. Muhammad) and his people Quraish: if he overpowers them then he is a true Prophet. So, when Mecca was conquered, then every tribe rushed to embrace Islam, and my father hurried to embrace Islam before (the other members of) my tribe. When my father returned (from the Prophet) to his tribe, he said, "By Allah, I have come to you from the Prophet (ﷺ) for sure!" The Prophet (ﷺ) afterwards said to them, 'Offer such-and-such prayer at such-and-such time, and when the time for the prayer becomes due, then one of you should pronounce the Adhan (for the prayer), and let the one amongst you who knows Qur'an most should, lead the prayer." So they looked for such a person and found none who knew more Qur'an than I because of the Qur'anic material which I used to learn from the caravans. They therefore made me their Imam (to lead the prayer) and at that time I was a boy of six or seven years, wearing a Burda (i.e. a black square garment) proved to be very short for me (and my body became partly naked). A lady from the tribe said, "Won't you cover the anus of your reciter for us?" So they bought (a piece of cloth) and made a shirt for me. I had never been so happy with anything before as I was with that shirt.Reference : Sahih al-Bukhari 4302
In-book reference : Book 64, Hadith 335
USC-MSA web (English) reference : Vol. 5, Book 59, Hadith 595 (deprecated numbering scheme)Does this mean memorizer of Qur'an (Hāfiẓ) is more preferred to lead Salat than religious scholar (Ālim)?