In this sentence, "even then" more or less means "at that particular time." For more, see, for example: https://www.merriam-webster.com/dictionary/even%20then. But there are close to 50 other accepted translations which you can use instead.
Making another complaint about the male voice. So dreadful. How are we supposed to learn correct pronunciation if this voice, even on the slow feed, says "tendy" rather than "tehdy"? On another exercise, the voice says "kupil" rather than "koupil". I know, we should know that there is no verb "kupil", and no word "tendy" - but it is really bad.