Brick is something man made. Babylon is built of man-made materials. They will not give Christ His rightful place as the head and the foundation of the church. There was no divinity in their plans. This represents another substitution.
Devilish spirits hold their doctrines together.
They are not of a divine origin, but man made. Bricks are something that man makes as a cheap, inferior substitute. We need to be ever reminded that behind every false teaching and every false doctrine is a spirit that propagates it. Those devilish spirits are out to seduce the souls of mankind. Spirits hold the systems together and hold people to their doctrines and systems.