The Chettiars established Chettinad in Chennai and the city has many palaces and temples.
Chettiars did not establish Chettinad anywhere. Chettinad commonly refers to a group of 96 villages (now down to 78) around the town of Karaikudi and Pudukkottai. That is about 400 kms away from Chennai.
When the British Government wanted to confer the title of Rajah on the most prosperous trader of Chettinad, they created a small principality (in effect a village) called Chettinad and made him the Rajah of Chettinad.
While the Chettiars abandoned the area in the 1940s but the place still attracted lots of tourists. However, many building have been torn down and their artifacts sold off as antique items.
Chettiars have not abandoned the area of Chettinad. We still go there to get married, to attend the local festivals and so on. We still have ancestral houses there, which we struggle to maintain. The area does not attract lots of tourists, unless you assume the masses who come on pilgrimage to the famous Pillayarpatti temple there.
The second sentence is true - many buildings have been torn down and their artifacts are sold off. I assume that the entire report was prepared by some one North of Vindyas with poor knowledge of South India and even poor googling skills.