Elaborate? I'm a mechanical nerd. I love to learn how this stuff works.
oh okay.
Lets start with some basics.
I am betting on a few things such as the seat for the drive gear gave out (free spin), the drive chain snapped, the teeth sheered from too much weight and poor quality metal (this happens in china so often that they literally import Pittsburgh steel for any mission critical needs as they know the American steel is not counterfeit or generally garbage), or the non maintained gearbox went bye bye. They probably removed the safety regulators because they are designed to detect and prevent this sort of failure. Think of it like disabling your knock sensors because they keep forcing the car into limp mode.
A case of "get it running now, we pay for real fix later, maybe".
They are probably reversible stairs, so there is no one way clutch. The sheer weight of the people on the escalators are what cause the speed that you saw. Think of trying to climb up a blanket that is put on a playground slide.