Actually no one did. Jesus said if you believe, you're saved, and no one approaches the father except through him, but that also leaves a lot of room for interpretation. The way he worded it doesn't make me think belief is the necessary minimum - rather, that such a minimum has been passed if you believe. When he said, except through me," that sounds like Christ the noun speaking, rather then Jesus/Yeshua the proper noun. It demands attention to the meaning of Christ.
Control and power were exactly the reasons for which books were put in the NT - moderated by a general good will and desire to adhere to the truth. But moderated only. That council of bishops was called by Constantine for the express purpose of homogenizing Christianity and making it the imperial religion. We actually still have Constantine's letters to the bishops, so you can check this. Before the nicean councils, different churches used different texts. There was no uniformity. Some texts are now called apocrypha, and were excluded, but they predate the bible and they were significant. They were playing politics, pleasing this and that constituency, setting up others for future fights.
IMO its very strange that more of the New Testament is Paul than Jesus. Paul the Jewish tax collector... For Rome... F it, that dude was a spy, an agent of the state. I don't buy his conversion story one bit... So... Bite me.