Why the Failure of the First Covenant?

The writer to Hebrews states very clearly that the first covenant was faulty. I read this and ask myself the question, "What happened? Did God make a mistake? If God is perfection, why did he institute an imperfect covenant?"

I believe the answer to that is contained in John Sailhamer's new book The Meaning of the Pentateuch. He says that the first covenant was instituted to demonstrate that we couldn't reconcile with God through adherence to his law because it is too high for us; we cannot attain it. This sets the stage for God ripping through the fabric of time and history in Christ. His covenant is perfect and will last.