My third son Ashley is in a Kit Kat ad just started playing in tele. He took a break from football in Sydney and being Nix supporter to film the ad over in Romania
https://www.youtube.com/watch?v=RZxnJ9VXlhg
They did a good job, but why film it in Romania? Surely Australia has hills and trees.
I'd say... cheaper crews, set, location, extras... Its pretty common to film ads in unusual countries.