Why were Leclerc, Hamilton, and Gasly disqualified from the Chinese Grand Prix?

The Chinese Grand Prix last Sunday had an unusual ending, with three drivers being disqualified, including both Ferrari drivers, Charles Leclerc and Lewis Hamilton, who finished fifth and sixth, but had then their points removed. Pierre Gasly, who finished eleventh, was also disqualified.

Why were they disqualified? As explained by Formula1.com, in the case of Ferrari's Leclerc and Alpine's Gasly, their cars were underweight. That violates Article 4.1 of Technical Regulations, which says that cars cannot weight less than 800 kg. Both cars weighed exactly 800 kg, but a fuel draining from a procedure meant that a little over 1.1 kg of fuel was removed from both cars, thus making them lighter than the rule.

Hamilton's situation was different: the skid wear was found to be below the minimum 9mm thickness required. Article 3.5.9 of Technical Regulations requires a minimum thickness of 9 mm for the plank assembly, but it was found be 8.6mm (LHS), 8.6mm (car centreline) and 8.5mm (RHS).

This decision means that Esteban Ocon, Kimi Antonelli, Alex Albon, and Ollie Bearman were promoted two positions, and Lance Stroll and Carlos Sainz were promoted one position and take some points, while also being great news for McLaren, who saw their two drivers in the podium on Sunday.

Ferrari issued an statement, explaining that Leclerc's issue was due to their strategy of only one pit-stop, which meant the tyre wear was very high, causing the car to be underweight. Meanwhile, they attribute Hamilton's issue to a misjudgement, accept the penalty and add that they had no intention of gaining any advantage. Alpine posted a tweet, simply saying that they accept the decision and move on to Japan (April 4-6).