Even things that his master Moses did not tell him... -
And if you ask: But why didn’t Moses command him to build the Mishkan first?
We might say: Moses mentioned the vessels first because, in truth, the vessels are more important than the Tabernacle itself… and one should start with the essential thing. However, when it comes to the actual construction, one should start with the Mishkan, because the Mishkan holds the vessels! So Betzalel, who was appointed to do the act of construction, understood that he had to make the Mishkan first.
But Moses, who was appointed to do the teaching, knew the whole scheme of the Tabernacle, and for the purpose of teaching, he began with the vessels first. But when it came to the notion of practical implementation, he forgot what it was that goes first in reality - until Betzalel came along and reminded him.
That is why Moses said, “You are in the Shadow of God.” For Moses was especially attuned to learning, but not to doing. Whereas Betzalel was a man of action. The general principle is that Moses’ knowledge came from study, because that was his special purpose. And in study, one begins with the essential things. But Betzalel’s special purpose was action, and so the knowledge that came to him was how to make things. And that is how Betzalel knew how to make the Mishkan.