Im no expert but from what a few people have said:
Q Why didnt the cameraman move to get a better shot?
A Because he was on a balcony the same as the ones you can see on the right
Q why such poor quality?
A Because in bulgaria they can't afford fantastic cameras and it was probably quite old
Q Why no sound and so compressed?
A Because their computer probably isn't brilliant either and its quicker to upload it if it's a smaller file.
Q Why did they zoom in then out?
A because if theyre anything like me, they like zooming and then they think about the quality getting crap and zoom back out again
I think its pretty convincing and theres no way there was string involved
As for CGI, maybe, but given the camera used and my opinion on the reson for the low quality, sureley if they were going to digitally edit it they
would have better equipment. Unless its a double bluff kinda thing...