Thanks for the tag. I might be wrong but looks like the oil here on the road is due to the flipped over truck itself. Maybe there was already oil on the road which might have contributed to this result. But For such a heavy truck to aquaplane or skid ; speed will be a factor as well. If there was oil already then it should have been cleaned up.
Remember a car or any vehicle can skid very easily on slightly moist surface. Reason being In some places, rainfall occurs so rarely that when the road does get wet, water mixes with the oil and grease that have seeped into the pavement, making the road extremely slippery. Due to the sharply reduced traction your chances of hydroplaning are even greater under these conditions. Maybe the road was slightly wet and the truck lost traction, Please read and understand this thread https://www.pakwheels.com/forums/news-articles-driver-education-safety/211982-hydroplaning-aquaplaning-driving-rain-hidden-danger-have-you-ever-experienced
Meanwhile if you spot any oil surface, you must inform NHMP or concerned authority immediately, so that a sand layer is used to make the roadways safe for travel. Road pavement is black and the oil seeps inside so its very very difficult to judge a surface that's too when you are driving. The best approach is, drive slow even slower then posted speed limit as soon as rain starts. As I said, the slight moist surface is the most dangerous..