السَّلَامُ عَلَيْكُمْ

The difference of opinion of Aqidah among the Sahabah(who we get our Aqidah from) is very little. This is because:

1. If there was an issue, the Sahabah would bring it back to the Prophet ﷺ.
2. There was little deviancy in their time. The deviancy that existed was primarily from the Jews, the statements of which the Prophet ﷺ either affirmed or rejected.

As the Muslims expanded, a few things happened.

1. Knowledge was harder to find because:
   a. The Prophet ﷺ passed away
   b. The companions were passing away.
   c. Scholars were passing away

Narrated Abdullah binAmr bin Al-`As: I heard Allah’s Messenger (ﷺ) saying, “Allah does not take away the knowledge, by taking it away from (the hearts of) the people, but takes it away by the death of the religious learned men…”(2)

2. Muslims were being exposed to different ideologies/religions. These included(but not limited to) the:
3. Jews and the Christians
4. The Fire worshippers
5. The idolatry of the Persians.
6. Buddhism and Hinduism

These two things started to affect the beliefs of the ignorant Muslims.

Sources:

1. Sahih al-Bukhari 100
   https://sunnah.com/bukhari:100