The Holy One Blessed be He told Moses (Numbers 20:24) ‘Aaron shall be gathered unto his people; for he shall not enter into the land’ . When Moses heard that he became weaker. Moses knew that Aaron represented the Right and he felt as if his right arm got broken. Then God asked him to take Aaron and his son Elazar so Moses would know that Elazar will replace the Right that his father is about to disconnect from.
“קַח, אֶת-אַהֲרֹן, וְאֶת-אֶלְעָזָר, בְּנוֹ; וְהַעַל אֹתָם, הֹר הָהָר”
“Take Aaron and his son Eleazar and bring them up to Mount Hor;”
“וְהַפְשֵׁט אֶת-אַהֲרֹן אֶת-בְּגָדָיו, וְהִלְבַּשְׁתָּם אֶת-אֶלְעָזָר בְּנוֹ; וְאַהֲרֹן יֵאָסֵף, וּמֵת שָׁם”
“and strip Aaron of his garments and put them on his son Eleazar. So Aaron will be gathered to his people, and will die there.”
The clouds of honor that protected the Israelites by the merit of Aaron went away when Aaron died and came back not by the merits of Elazar his son but only for the merits of Moses.
“וַיַּעַשׂ מֹשֶׁה כַּאֲשֶׁר צִוָּה יְהוָה וַיַּעֲלוּ אֶל הֹר הָהָר לְעֵינֵי כָּל הָעֵדָה”
“So Moses did just as YHVH had commanded, and they went up to Mount Hor in the sight of all the congregation.”
The entire process of ‘stripping’ Aaron from his spiritual connections and transferring it to Elazar was ‘in the sight of all the congregation’. The Zohar explains that all the people could see the transfer of light from father to son so they won’t say that Aaron died by the hands of Moses.