They started out as missionaries. After studying Chinese in China, they made friends with dignitaries and worked as translators. Some of them went back to sort out the dictionary. (including many languages, not English in the early days, but Portuguese and Russian, related to history. )

After the First Opium War, there was a large-scale English translation. At that time, the translation mode adopted was similar to the way of translating Buddhist scriptures in the Tang Dynasty, that is, foreigners who knew Chinese orally translated them, and then our scholars took notes and polished them. At the same time, some scholars understand English and translate directly. But after all, it is a minority.

Of course, there are also many monographs that introduce the history of translation in detail. You can refer to the monograph on translation history. I'm just sketching here.