Wonder why God instructed Moses to build a tabernacle. God could have built it Himself. Here is a possibility. Knowing the people had brought other gods with them from Egypt God wanted his chosen people to focus on Him so He could bless them more. So He had them donate their treasures (those who had it in their heart to do so). He had them take those treasures and make a tabernacle where He would meet with them. And where their treasure was their heart would be also. Making an ornate and expensive cathedral is not to impress God or to attempt to glorify Him with physical stuff but by giving of their treasures the people would no longer need to be worried about hanging on to that stuff. Always trying to make sure their treasure was safe and secure from loss, damage, or theft. Once they gave it away they could still enjoy the sight of it whenever they came near to God and hopefully come to realize that God is even more valuable than the treasure had been to them.