Without going into a lot of detail, there's a certain procedure that must be followed when an F1 car crashes on track. If the procedure had been followed as written in the rule book, the race would've finished under a safety car and the driver who has won the previous 4 championships would've won his 5th in a row and 8th overall.
But the governing body of the sport decided to be a little lax on the procedure and wrapped up the safety car early, allowing both drivers to race head on on the last lap of the race, and the 2nd driver had a massive advantage with his tyres and ultimately won the race.
The controversy stems from the fact that the governing body seemingly decided who the champion should be by ending the safety car without completing its own procedure properly.
