THE STONEHENGE HIDDEN LANDSCAPE PROJECT. The reason for the recent discoveries near Stonehenge is that there is now a Stonehenge Hidden Landscape Project. Here is its website, which shows the scope of the Project—“a collaboration between the University of Birmingham, the Ludwig Boltzmann Institute for Archaeological Prospection and Virtual Archaeology, Vienna and its international partners, the University of Bradford, the University of St Andrews, and the ‘ORBit’ Research Group of the Department of Soil Management at the University of Ghent, Belgium.”
Here is a description of the discovery of Superhenge from the official site. Note that two of the scientists quoted point out that the Stonehenge site had been extensively studied for centuries before the recent discoveries.