According to Chief Justice Burger, why was the crèche display constitutional?

"The exclusively Christian standalone nativity scene displayed on the courthouse lawn amounts to a monument to Christianity that conveys the unmistakable message of governmental endorsement of religion, and Christianity specifically, in violation of the Establishment Clause of the First Amendment," said Monica Miller, an attorney with the Appignani Humanist Legal Center.

In a statement, Abbott made a counterargument that the nativity scene wasn’t "standalone" and had other elements.