The famous Singaporean politician Lee Kuan Yew to whom you refer was given the English name Harry by his parents. The poster you're quoting isn't themselves claiming to be LKY.
There's no pronoun for that sentence, so it's left undefined who it's talking about. It doesn't mean the poster. It also doesn't really matter, if one former Singaporean politician dropped their "first name" then it's being used as an example that others may too.
It means that LKY himself stopped using the name Harry, for whatever reason. His (LKY) Wikipedia article states when, but not why - it cites his autobiography so that may be a useful source if you are interested to learn more.
