How does apostolic succession or Nicea prove God's approval?

This is an interesting question, and although I concur with your assumptions in your explanation, I still wonder what it is you are really wanting to know by asking this question? So I shall just give you my take on this whole situation as I see it. First of all there was no Apostolic succession of which you speak. Before all of the Apostles were killed a man, whom the Catholics say was a Bishop, stepped forward after the death of Peter and assumed the position of head of the Church, trying to replace Peter. However, if he was a Bishop he only had authority over a single congregation, he could not take over the Church, except under his own authority. Jesus Christ ordained 12 living Apostles to guide and direct the Church by revelation, after he had ascended into heaven.

The Bishop who supposedly replaced Peter as head of the Church was named Linus. Strangely, there is no evidence that Linus was ever ordained a Bishop by Peter as the Church claims, and yet that Church still functions today as the largest and oldest organized Christian Church in the world. And they claim their Apostolic succession took place through their Bishops. The Apostles were not Bishops, they were Apostles. Apostles call and ordain Bishops, Bishops do not call and ordain Apostles. Therefore the bottom line is after the Apostles were taken from the Church,(killed) their Priesthood authority also went with them. The keys of the Priesthood were also taken from the earth. Which means even though there were still Bishops in the Church, without the keys of the Priesthood on earth, none of them was authorized to use their priesthood, for any reason.

Which means all ties from heaven and the Church were severed, when the Apostles were killed. So for over 2000 years the Catholic Church and all of the Christian Churches today have been operating without any authority from God. That doesn't mean they are not sincere in what they do, but it simply means God does not recognize anything they do in Christ's name. The Bible prophesied that in the last days "All things would be restored." So if you want to find the true Church look for a Church which claims to be a restored Church. And there is one key the scriptures say will occur, that is, it will be restored by Jesus Christ coming back for that purpose. This scripture can be found in Acts 3;19-21..."Repent ye therefore, and be converted, that your sins may be blotted out, when the times of refreshing shall come from the presence of the Lord; 20 And he shall send Jesus Christ, which before was preached unto you: 21 Whom the heaven must receive until the times of restitution of all things, which God hath spoken by the mouth of all his holy prophets since the world began." I have given you several clues, go find the true Church!

Nicea proves one thing, that "truth" was determined by a vote. Did you get to the part where 2 people on the main opposing viewpoint were murdered? That's why the Pauline doctrines including the trinity won. The other side was short a couple of guys.

EDIT NOTE: No, The Bible wasn't around before then. There were hundreds of documents being used by Christians and they had assorted sects even back then. The persecutions had nothing to do with the Bible itself because it hadn't been compiled yet. Having a settle set of define beliefs and scriptures was the primary task of the counsel.

If you dig deeper than versions of the events than accounts use expression like "divinely inspired" you're going to find some things that Christianity wants to pretend never happened. Dig deep. Be thorough. What you will find is pretty ugly.

You do have to understand that evil men will try to gain power by any means. That is what is so evil about joining churches under one umbrella or, as some call it, the Ecumenical Movement. They'll join everyone together only for the purpose of gaining power and influence over them.

This is why churches should remain - as the Bible teaches - independent of one another.

The Mega Churches of today are little more than faintly veiled outreaches for the Antichrist's One World Religion. The individual, much like our communist governments today, have to bow for the "good of the whole" while losing every bit of their freedoms and rights for which many good men have shed their blood to bless their descendants.

When it comes right down to it their just power grabbers who deny the apostles in practice but serve them only in name because of the power that it gives them.