Perhaps the greatest conundrum of sidrah Terumah is the seeming incongruity of sliding from sublime revelation to a collection of construction materials. Israel emerged from Egypt, met God at Sinai and committed itself to the Covenant. Mishpatim ends with Moses re-entering the fiery realm where God’s Presence could be grasped.
Terumah sets about the construction of the Tabernacle. In place of grandiose vision, we encounter an earthy array of metals and cloths, planks and sockets. For Nachmanides, the change of tone expresses a shift of modality as we leave the high of revelation and focus on taking that experience with us via the Mishkan. Inspirational highs help point the way for us; but they evaporate quickly and cannot be recaptured without painful attention to detailed construction.
A second, midrashic approach suggests that Terumah is presented out of chronological order. The Tabernacle served as an antidote to the Golden Calf. Romantic, ecstastic relationship has been violated; now we explore plan B, the Tabernacle. But why violate chronology?
Avivah Gottlieb Zornberg suggests that the Torah teaches us the Tabernacle was always planned, because our pagan passions are always lurking. Man desires tangible contact with God as a mammal yearns for physical contact. First Torah reveals the plan, then it returns to the episode that brought the hidden subconscious desires out in the open. The physical Tabernacle helps us convert those passionate instincts for the good.
Perhaps the approaches dovetail. The first tells us that passions can never substitute for hard self-development. The second tells us that such passions, once converted, are our greatest spiritual asset.