But the defining moment that triggered the Monza surprise was when race leader Lewis Hamilton was handed a 10-second stop-go penalty for entering a closed pitlane to change tyres.
Such a rules breach is deemed a serious offence, and it took Hamilton out of contention for the win on a day he looked set to cruise to victory.
Here we look at the background to the incident that changed the shape of the race, and explain the circumstances.
Why was the pitlane closed?
Kevin Magnussen had been battling from the back of the field, after picking up front wing damage on the opening lap that had required a replacement. However, after 17 laps he ground to a halt with a suspected power unit problem on the exit of Parabolica.
After pulling over next to the barriers on the right side of the track, the FIA felt that the best option to retrieve the car was to push it forwards down the pitlane.
So with marshals potentially exposed to cars as the moved Magnussen, F1 race director Michael Masi decided that the best option was to close the pitlane and to bring out the safety car.
Why wasn’t Magnussen’s car pulled back behind the barriers?
The Safety Car Lewis Hamilton, Mercedes F1 W11, and Lance Stroll, Racing Point RP20
Photo by: Charles Coates / Motorsport Images
When Magnussen’s car came to a halt, he had…