Will a person be rewarded for their intention to complete the Qur’an in the Witr rak’ah, even if they were unable to do so due to a legitimate شرعي excuse, and will the one who was the cause of this intention also be rewarded?

Whoever intends an act of obedience and resolves firmly upon it, then is prevented by an impediment, will have its full reward written for them. This is based on the Prophet's (peace be upon him) saying: "Indeed, Allah has decreed good deeds and evil deeds, then He clarified that. So, whoever intends a good deed and does not do it, Allah writes it down for him as a full good deed..." [the rest of the Hadith]. Therefore, whatever good deed you intended and an excuse prevented you from performing it, its reward will be written for you. As for the video publisher, the reward for guiding to good will be written for him, due to the Prophet's (peace be upon him) saying: "Whoever calls to guidance will have a reward like the rewards of those who follow him."