LKY was a native Baba Malay speaker. He couldn't speak a single word of Hakka or Mandarin until he became Prime mInister. He had no love for the language; learning it was a political expediency.
He did not neglect Malay, but he did not emphasize Malay as a lingua franca, preferring to use English as the official lingua franca, because he feared the bumiputra-isation of Singapore (his unfulfilled dream was leading a Malaysian Malaysia, Singapore was just a watered down mini-version).
The Speak Mandarin Campaign was political: it wasn't about currying favour with China (in the '70s we were China's master, not the other way round), it was about his fear of the dialect clans getting too strong and independent leading to support for charismatic dialect-speaking opposition candidates like Lim Chin Siong (Hokkien) and later, Low Thia Kiang (Teochew). All dialects were banned on radio and TV; SBC dubbed all HK dramas in Mandarin. His aim was to eradicate dialects - linguicide - to shore up the PAP's power and to prevent the resurgence of another Barisan Socialis.