Nothing to do with a runway - journos just think any pavement at an airport is "runway."
From the surveillance video - even with bits edited out - it
does look like they were fooled by the doubled-up parallel taxiways into turning too soon onto what they thought was ramp, but was a second strip of grass. That is also a 2-meter hole in the ground!
But nothing (yet) rules out a wind gust or sudden tiller problem.
In this picture:
https://c2.staticflickr.com/4/3071/2...34e02b9686.jpg
...the accident occured lower right, where the medium-gray taxiway meets the lighter ramp pavement. The fact that the "ramp"-colored pavement extends down the taxiway a little way could have contributed to confusion as to where the edge was - at dusk, and with a brightly-lit terminal in the background to suppress night vision.
I'll be interested to see what the final report says.