The Catholic Church decided which books went in the Bible. Books such as the Gospel of Judas, Shepherd of Hermas, etc we’re excluded based on their teachings and the authority of the Church.
And some books were written by Disciples, not Apostles. Big difference.
https://www.catholic.com/encyclopedia/bible
And those disciples were relaying their 1st hand reception of the Apostles teaching.
No they didn’t. Athanasius In his 39 festive letter identified the current canon well before the the counsel of Carthage. And he presented it as already common knowledge.