Not the conspiracy theory part, the part where you think it is impossible for it to drop that much that fast. Ether had an incident like this in August where it lost almost all its value on that exchange in seconds. Granted they didn't have safety mechanisms built in to stop all the stop losses from triggering but something similar could've happened here ("could have" as in anything is possible).
Example: BTC spikes on Luno to R177k and somebody makes a HUGE sale to cash in. Naturally the price drops so somebody else sells there and so forth. The system could get overloaded with all the transfers happening or maybe something kick in to stop a crash.
...or the site just threw a Takealot and crashed.
Point is, these things can lose a lot of value very quickly