Gaon Yaakov on Vayakhel

The Gemara (Berakhot 55a) presents the following conversation between Moshe and Betzalel:
When G-d told Moshe to tell Betzalel to make the Mishkan (structure), Aron (ark) and rest of the vessels, Moshe switched the order and said, "Make the Aron, vessels, and Mishkan."
Betzalel replied, "Moshe Rabbeinu, it is the way of the world to first make a house and then to place within it vessels. You tell me to make the Aron and vessels before making the structure. These vessels that I make, where will I place them? Perhaps G-d told you that I should make the Mishkan and then the Aron and vessels?"
Said Moshe, "Were you perhaps in the shadow of G-d (betzeil Ei-l, a play on words using the name Betzalel) and knew what he was saying?"
There are several striking difficulties with this passage.
1. Why did Moshe switch the order from what G-d instructed him?
2. What was the "argument" between Moshe and Betzalel concerning the proper order?