Commentators often focus on the phrase, “in their midst”. We might have expected “in its midst”. But what the Torah emphasises is the people who made it and worshipped in its midst. A place of worship can become an empty shell unless it has a living congregation. But there are other lessons – for example, why require a sanctuary at all? Doesn’t Isaiah say (66:1) that the whole universe belongs to God, so why put up a specific building? Isaiah also says, “The whole earth is full of His glory” (Isa. 6:3).
Sforno suggests that everything changed after the incident of the Golden Calf. The concept of a ubiquitous God was too sophisticated. The Israelites needed a physical focus. But the sages say the mikdash was always part of the plan. The issue was timing. Not, “Why have a mikdash?” but “when shall a mikdash be built?” The answer? “When mankind shows that it needs a symbol”.
Without visible symbols, religion is too difficult for many people. Freedom is a basic ethic, but without Pesach it might evaporate. God’s presence is everywhere, but it is harder to grasp without waving the Four Species on Sukkot to show that He is in all corners of the Creation.