Reb Eliezer: “It says veosu li mikdash veshochanti besocham, create a holy tabernacle and I will rest among them. It does not say besocho, in it as Hashem is everywhere so He rests in each one of us.”
If that would be pshat, there would be no need for a mikdash for us to be told that. The same could be said pre mikdash. אלא מאי that is not pshat. The pshat is that through the mikdash, HKB”h will rest among Bnei Yisroel, since the mikdash is located among us.