Why does it say "v'Chol ha'Am"?
Malbim: It was not only the chosen elders, rather, everyone.
What is "Ba'alei Yehudah"?
Rashi: It is Kiryas Ye'arim, like it says in Yehoshua (15:9) "Ba'alah Hi Kiryas Ye'arim" and in Divrei ha'Yamim I, 13:6 "Ba'alasah El Kiryas Ye'arim." 'Ba'al' refers to a plain (refer to 5:20:1:1).
Why does it say "mi'Ba'alei Yehudah"? It should say El Ba'alei Yehudah, for the Aron was there [and they went to bring it], and so it says in Divrei ha'Yamim I, 13:6 "Ba'alasah El Kiryas Ye'arim"!
Rashi: They had gathered there to bring the Aron, and now they came from there. Radak - the verse is abbreviated; it omits that they had gathered there to bring it.
Why does it say "Asher Nikra Shem Shem"?
Rashi: The Aron was called a name. What is the name? The name of Hashem Tzevakos is on it.
QUESTIONS ON RASHI
Rashi writes that the Aron was called on the name of Hashem Tzevakos [Yoshev ha'Keruvim] is on it. Why is this only here?
Radak: Hashem's name was sanctified through it when it was in Sedei Pelishtim.
Malbim: This hints to Uza's death for his sin in the continuation. Since the Keruvim are a Merkavah for Hashem, the ones who carry it must resemble the bearers of the Merkavah above, i.e. [angels] with [the form of] a human face, and not via an ox 1 and donkey. Also the people who carry it must be from Levi, which Hashem chose!
The bearers of the Merkavah above have four faces, with the forms of a person, lion, ox and eagle (Yechezkel 1:10)! Perhaps the human face is primary. Alternatively, each has a human form, unlike the oxen that David used to take the Aron. (PF)