Becouse Jesus clearly said so.Which he never did talking about being God - only suggested that.
Here,what Jesus said about himself and Peter:
Matthew 16:13-20
Peter Declares That Jesus Is the Messiah
13 When Jesus came to the region of Caesarea Philippi, he asked his disciples, “Who do people say the Son of Man is?”
14 They replied, “Some say John the Baptist; others say Elijah; and still others, Jeremiah or one of the prophets.”
15 “But what about you?” he asked. “Who do you say I am?”
16 Simon Peter answered, “You are the Messiah, the Son of the living God.”
17 Jesus replied, “Blessed are you, Simon son of Jonah, for this was not revealed to you by flesh and blood, but by my Father in heaven. 18 And I tell you that you are Peter,[
a] and on this rock I will build my church, and the gates of Hades[
b] will not overcome it. 19 I will give you the keys of the kingdom of heaven; whatever you bind on earth will be[
c] bound in heaven, and whatever you loose on earth will be[
d] loosed in heaven.” 20 Then he ordered his disciples not to tell anyone that he was the Messiah.
Here,Peter get keys to Kingdom,which basically is popes power.And,Jesus HIMSELF declared as nothing more then Messiah,not God.
If i were REAL protestant,i would belive in popes power,but not Jesus being God.But,they were created to gave church and its property to princes,so we have what we have.
Living weapons for long excint rulers.
Here,another Paul :
1 Thessalonians 2:13-20
13 And we also thank God continually because, when you received the word of God, which you heard from us, you accepted it not as a human word, but as it actually is, the word of God, which is indeed at work in you who believe. 14 For you, brothers and sisters, became imitators of God’s churches in Judea, which are in Christ Jesus: You suffered from your own people the same things those churches suffered from the Jews 15 who killed the Lord Jesus and the prophets and also drove us out. They displease God and are hostile to everyone 16 in their effort to keep us from speaking to the Gentiles so that they may be saved. In this way they always heap up their sins to the limit. The wrath of God has come upon them at last.[
a]
Paul’s Longing to See the Thessalonians
17 But, brothers and sisters, when we were orphaned by being separated from you for a short time (in person, not in thought), out of our intense longing we made every effort to see you. 18 For we wanted to come to you—certainly I, Paul, did, again and again—but Satan blocked our way. 19 For what is our hope, our joy, or the crown in which we will glory in the presence of our Lord Jesus when he comes? Is it not you? 20 Indeed, you are our glory and joy.
Again,God is God,and Jesus is Messiah and Lord,not God.