The point is the language, not the content, I assume. Although dictionary + grammar textbooks would have been better. I'm also not sure about thousands of lang

The point is the language, not the content, I assume. Although dictionary + grammar textbooks would have been better. I'm also not sure about thousands of languages (the goal being all of them). Throughout history, there may have been a hundred of lingua francas. A few hundred tops. We also see a constant desire of people to leave writings in the most popular language of the era. It makes sense, too: they want the largest percentage of people to be able to consume their writing. Creating dictionary pairs + grammar textbooks + science textbooks for a (still) large but limited number of languages popular now and in the past would be more beneficial to future linguists.