Idk who exactly said it, but it was in reference to Islam and Mohammed: The earliest roots of a religion like Islam or Christianity are often very different to what later comes after it. Something about Mohammed being a succesful conqueror and rather than him establishing a religion, it was his succesors who were really responsible for making it a religion.
Anyway I am especially interested in who and when turned Jesus from a Messiah to god's son, which was then constructed into the trinity.
Who was responsible for that view? How did other christians or outsiders react to it? Why was this more popular than arguably the more logical position of a Messiah?
And besides the divinity of christ what other things "changed" before ultimatively the council of nicea? (or if you know of a better cut off point, feel free to talk about that)
I would characterise the field as having a few major views on the topic, but they fall roughly into two camps.
Others have already referenced Bart Ehrman’s view, which is not unrepresentative of a slice of scholarship. Certainly he is among the more accessible popular writers that you could get into in this area. Ehrman’s basic thesis is that that earliest views of Jesus within emergent Christian communities evolved from his historical situation as an apocalyptic prophet, through messianic associations and identification as an intermediary figure (like an angel or similar), developing by the late 1st century (or even later for other scholars) to a view of him as divine.
Ehrman’s thesis puts most of this development prior to the writing of the New Testament, so his argument in “How Jesus became God” is an attempt to argue that traces of that development are attested in the New Testament corpus. A conservative response volume was put together, “How God became Jesus”, by a collection of scholars who tackle some specific points of Ehrman’s theory.
Another group, jokingly called the “Early High Christology Club”, argues that a very ‘high’ view of Jesus existed in the earliest generations of Christians. Larry Hurtado is probably one of the most high profile representatives. Generally they reject the thesis that Jesus’ status as divine ‘evolved’ over a significant period of time, arguing that Jesus was treated in a kind of ‘binitarian’ (Hurtado) fashion wherein his ‘identity’ (Bauckham) is included in the identity of God.
Whichever position you take, it’s clear that at least some, if not the whole, New Testament corpus, treats Jesus as divine in many respects, and applies divine honours and divine titles to him. This, let me point out, does not depend upon the phrase ‘Son of God’, which already has currency in Jewish circles as an Old Testament title for the king. As you move into the second century Christian writings, Jesus is likewise largely treated as God, though the ‘specifics’ of how that works are not very well ‘worked out’.
I’m happy to answer follow up questions on this and related topics here. I’ve already named a few scholars, but I can point you to some specific works if you want to read on.
r/AcademicBiblical might be a better place to ask this question.