They are calm, but in the western world people have to think of their 15 seconds of social media fame and the obligatory compo claim and thus have to dramatise things.
I find African people to be very pragmatic and no nonsense people. If this had been in Europe or the states then the state in the cabin would have been somewhat different, I can promise you that.
The masks will automatically deploy at 14,000 cabin altitude. The pilots can manually over ride and deploy them all or the cabin crew can use manual release tools in order to release them should the need arise. This could explain the sporadic deployment of them.
If TK did know, and cancelled their flight, and then subbed it to someone else, then that is pretty sickening stuff. Certainly another reason to avoid them.