The Latinate names were given and popularised by Jesuits writing about China when Latinising names (and writing in Latin) was the norm. It's the same basic reason we have Averroës (ابن رشد‎ ibn Rusd), Avicenna (ابن سینا ibn Sina) and Maimonides (משה בן-מימון‎ Moshe ben Maimon).

Laozi, on the other hand, was poularised in the West through translations like that of James Legge in the 1890s when Latinising names of "Eastern" figures wasn't so common (and in part because Legge wasn't writing in Latin anyway).

It's as simple as those being the forms used when the figures became known.

You'll note that lesser known figures like Yang Zhu (楊朱) or Xunzi (荀況/荀子), if they're known at all, are known with modern Mandarin spellings.

Post removed per subreddit ban.