“Innā fataḥnā laka fatḥan mubīnā”
“Indeed, We have granted you a manifest victory.” (al-Fatḥ 48:1)
God sometimes uses first-person plural forms such as “innā” and “fataḥnā.” In this context they express majesty; they do not imply multiple deities. A singular explanatory statement can clarify that the acting Lord is one, while preserving the exalted plural in recitation.
Likewise, “innā la-qādirūn” (al-Maʿārij 70:40, excerpt) speaks of the power of the one God. The speaker and the rhetorical form must be distinguished.
This is a specific rhetorical use of first-person plural, not an invitation to treat every plural noun or pronoun in the Qur’an as a plural of majesty.