Well, I was only 1 in 1976...
But the short version is, there was a pile-up on the first lap, at, I think, Paddock Hill Bend, where James got taken out. He got the car back to the pits for the restart, but via an unauthorized route, so he got thrown out. Apparently the reason given was that the car wasn't actually on the circuit when the red flag was thrown.
The crowd were furious, and staged a sit-in on parts of the circuit, throwing beer cans and bottles all over the place and shouting "We want Hunt, we want Hunt..." This lasted a fair while, by which time, McLaren had managed to fix his car and get it back out onto the grid. Fearing a riot, he was allowed to race despite a protest from several teams, and actually won.
Only to be thown out AGAIN later...
And the race win given to Lauda instead. If Hunt had kept the win, it would have changed the whole outlook of the 1976 season.