Don't see why anyone is surprised by this. There's a younger generation in Singapore who happily choose to fly the ME3 and LCC's over SQ.
That leaves SQ reliant on a pool of loyal customers who are willing to pay a lot more for slightly better quality - 1) corporate expense customers and 2) older Singaporeans who will not travel on any other airline. The former is static and the latter is shrinking.
What SQ can do about it is more difficult. It's hard to fight demographics. They need new ideas, but history suggests this is very unlikely. Not surprising as the formula of Singapore Girl + modern fleet has worked for the last 40 years.