Hope this helps to clear the air what is happening. Companies delisting in a down turn means that they know that it is undervalued and they can buy up their own shares cheaply. It means they pocket all the profits which are the dividends. When the market picks up, they will float their company again (IPO) and make a second killing. Listing in another market is to snare to a new group of naive people who have no background. This used to be frown but many business which are controlled by an individual or by a family tend to do this as they have inside of what the company is worth. In the past these companies were the favourite of mom and pops who like to play penny stocks.
You are right. Some delist because they are doing well and find that their company shares are undervalued. One such company is Wing Tai Holdings. Its assets per share is $4.04 but is trading at $1.92 now. The company is cash rich and has the ability to buy back all the chares and go private. It has one predominant share owner. It is a prime candidate to take the company private, especially when some of its prime properties remain unsold and it may have to pay $110m to the govt.
But most of the 58 delisted companies are unlike Wing Tai. Most are like NOL which became insolvent and went bankrupt. These companies just close shop and ceased to be a going concern. These companies reflect the health of the Singapore Share market