I'd say based on the very limited evidence available thus far that Mr. Pattern is Full has it about right; some imperfection in that area, possibly long standing, looks to have caused a progressive (and thankfully relatively slowly propagating) pressurization leak, resulting in the failure of the skin and disappearance of the fairing - looks more like a progressive tear through originating from a small source area. Interesting to see the investigation result when it comes out.
Very well done to the crew; trained for it may be, but its always different when you're not 100% sure if there are more little surprises to follow!