Why did the Companions and the Successors need another collection of the Qur’an in Uthman’s Mushaf, if the Mushaf of our master Abu Bakr was already in existence, and why did errors in recitation (Lahn) and differences occur?

The collection of the Quran during the time of the Prophet, peace be upon him, involved writing down the verses and arranging them in separate pieces. As for the era of Abu Bakr, it was a transcription of the Quran and its writing into a single volume (mushaf) with the verses arranged, the purpose of which was to record the Quran and preserve it from loss. In the era of Uthman, it was a transcription of what was in those scrolls into one authoritative mushaf, and the copying of multiple mushafs from it to be sent to the Islamic horizons to unify Muslims after the spread of grammatical errors (laḥn), foreign accents (ʿujmah), and differences in readings. So, he ordered the burning of all other copies.