Flying with 4 people on board, full fuel and a warm evening - at those limits a C172 handles like a bowl of porridge.
Railton
How warm? Maybe a density problem? Temperature increases cause drastic performance declines, and with the plane at capacity, hhhmmm. Wouldn't be the first pilot to make that error.
Judging by the debris, we might not ever know what happened. What I do know is that it's horrible that four young people are dead. Lots of vibes to their families.