On that day Yahweh magnified Joshua in the sight of all Israel; and they feared him, as they feared Moses, all the days of his life.
The immense importance of the ark of the covenant also shines in passages such as this.  And where, pray tell, did this ark of the covenant come from?  It is starkly clear to every student of the Bible that Joshua is but a continuation of the historical books called the Pentateuch.  If one wishes to know all about the ark of the covenant, he may surely read it in the Five Books of Moses, and it is no wonder that Moses' successor was the official custodian of that ark and all that it represented.