It was setting them up for a precedent-setting legal decision in a higher court that may very well have not gone the government's way.
>they couldn't proceed without lying to the court
You're assuming that this mysterious third party that showed up the day before the initial hearing with a method to crack the phone actually exists, and that this method was successful. That is certainly a possibility, but it is also possible that they never intended to see this through and hoped that they could intimidate Apple into doing exactly what they wanted.