Why does the Torah ascribe the construction of the Aron to Betzalel?
Rashi: Because he put into its construction more than all the other Chachamim, it is called after him.
Ramban and Seforno: Because he actually constructed it. Refer to 36:8:1:1.
R. Bachye: Because the Aron was the most sanctified of all the Keilim and Betzalel who was filled with Ru'ach Elokim ? Chochmah, Tevunah and Da'as, was the most fitting person to manufacture it ? and because it needed to be made with the deep Kavanah that only he was capable.
Da'as Zekenim, Rosh, Moshav Zekenim and Ba'al ha'Turim (in 38:1): Because his name is the acronym of "be'Tzeil Keil" (in the Shadow of Hashem) - and 'Tzeil Kel' rested on the Aron (He knew the secret of the Aron and Merkavah, because the Aron corresponds to the Kisei ha'Kavod - Moshav Zekenim and Ba'al ha'Turim). 1
Why did Hashem command that they make the Aron specifically of "Atzei Shitim"?
R. Bachye, Da'as Zekenim and Rosh: Because Hashem foresaw that they were destined to sin at Shitim (regarding Arayos and idolatry). 1 Therefore He established [the Aron of Atzei Shitim] to atone for the episode 2 in Shitim. 3
A. Because it was the best type of wood for the Keilim, and b. Because it was available. 4
See Bamidbar 25:1-3.
Rosh - Hashem prepares the cure before the illness.
See R. Bachye at the of the Parshah, who explains that, like the Gemara states in Menachos 110a with regard to Korbanos, it is a great Mitzvah to study the intricacies of the Mishkan and its measurements. And he supports this with Pesukim in Tehilim 48:13-15 - "Sobu Tziyon Vehakifuhu ? " - and elaborates.
Why did Betzalel make the Aron before all the other Keilim?
Da'as Zekenim and Rosh: Because, just as light was the first creation, as implied by the Pasuk in Tehilim 119:130 "Pesach Devarecha Ya'ir" - so too did Betzalel first make the Aron, since it contained the Torah, which is called light. 1
As the Pasuk writes in Mishlei, 6:23 "Ki Ner Mitzvah ve'Torah Or".
Where were the Luchos placed before Betzalel made the Aron?
Refer to Devarim, 10:1:3:1-3.
