The main requirements for the Imam of Jama'ah are:
1. He be well versed in the rulings of fiqh and prayer in particular.
2. A man of piety and righteousness, with inner taqwa, high moral standards, and 'adalah, which means he does not commit regular sin.
3. His pronunciation and recitation is accurate.
4. Other things mentioned in the fiqh books.
If there are numerous people who broadly have these main requirements, then the person who is more learnt, or with more taqwa, or better recitation, is presented as the Imam Jama'ah.
And Allah knows best.