Bit harsh to judge without having any real trackside information. So many factors can contribute to the back end coming lose like that.
He could have come around that bend at the same speed the previous 15 times without issue and then this time it breaks lose...flat spot on the tyre, something on the track etc. When it starts to come around your dealing with an 1800kg saloon with probably an extra 160kg in the back seats, it's not a sports car.