After the toll KL bound? Is that after the Bentong turn off?
That corner is the second left tight curve after the right steep climb right after the toll?
Bro, think your car suffered a weight imbalance when you "threw" it over the crest of the hill. This was what caused Diana's Merc to crash in that tunnel Paris, only that instead of 200km/h speed that her driver lost control from, yours was a combination of wet road, tight corner, slightly faster than safe speed and possibly bad timing of your reaction in the form of steering-brake input.
I know that hill at around 90-100 in the dry, the car feels light. I theorize that near the crest your rear wheels lost grip, and because all four wheels are still rotating at the same speed, because possibly you weren't braking or accelerating at that point, the DSC couldn't detect a problem.
Then your rear comes around and you reacted and possibly jammed on the brakes or there was oil on the road. Either way, there was something at this point that made the spin worse and beyond the reach of what the DSC could recover from. Your front wheels were weighed down by both the engine and you and had the grip, but there was no one else in the car weighing down your rear which was flying in the air and swinging around you like a Porsche 911. And you were on the downhill slope, which was the final nail.