The question is how ‘theology’, as a systematic category of its own, started in Islam. With few exceptions, a lot of scholarship attributes this, disproportionately, to the exposure of Islam to other religions and regions – Hellenistic culture, Christian thought. Usually things that would sustain the West as somehow the center of the universe – and render Islam agency-less.
The story of Islamic theology begins with us as self-reflecting beings, the Qur’an and the Prophet’s (saws) sayings and actions. The history of systematic discussions about Islamic theology starts with the question of Imamate and succession to the Prophet (saws). A good deal of early theological works are concerned with the question of Imamate – not only ‘shia’ texts. Check al-Mughni by Qadi Abd al-Jabbar. Check the discussions that were spurred by the Khawariji insurrections.
The idea espoused by some people that Muslims who lived in the Prophet’s (saws) lifetime did not have a ‘science of theology’ because the Prophet (saws) was a final authority on theological matters (and hence things did not need to be ‘discussed’) strikes me as pretty unthoughtful? We are talking about a community of converts who are constantly trying to understand what it means to believe in One God. They were either polytheists or monotheists of one sort beforehand.
The Qur’an and the Prophet certainly have authority, but I don’t see how this authority bars people from ‘thinking’ about God. They may not be speculating, but they are certainly reflecting – they have to. Faith is not a matter of emulation. Moreover, the Qur’an is replete with moments that captures these communal and individual reflections, and provides responses to them.