THE PLT STATED THAT DRG THE LANDING, THE ACFT STARTED DRIFTING TO THE RIGHT & HE APPLIED LEFT BRAKE WITHOUT GETTING A RESPONSE. SUBSEQUENTLY, THE ACFT GROUND LOOPED TO THE RIGHT, THE LEFT MAIN GEAR COLLAPSED & THE ACFT NOSED OVER. AN EXAM REVEALED THE LEFT BRAKE LINE HAD FAILED, BUT THE FAILURE APPEARED TO BE FROM OVERSTRESS WHICH OCCURRED DRG THE GEAR COLLAPSE.