I think this is a consequence of LKY's social engineering skills especially regarding education and particularly the overzealousness in crushing dialects in order to force Sinkies to 'speak good Mandarin'.
High irony too, considering LKY himself was a Hakka 'banana' mongrel who kissed the Poms' arse during the colonial days, and never had an acceptable proficiency of Mandarin.
Just look across the Causeway and see the Chinese folks there carrying on as usual when it comes to Chinese language education and dialects, minus LKY's meddling. They are far more fluent in the languages. And the English proficiency of the younger urban dwellers isn't too bad either.