In the case of English, "she" was used much less than "he", and it still hasn't caught up. In Russian, it looks as if the translation of "he" almost didn't exist, until around 1915. What happened?
Actually, the year is not "around 1915", but the beginning of 1918 when the orthography reform began. Before 1918 "он" was written as "онъ", and naturally before 1918 "он" was not used. Have a look:
After 1918, Ъ at the end of words after "hard" consonants was used mainly by emigrants in their printed publications. All the instances of "он" used before 1918 that Ngram Viewer shows in its graphs are actually mistakes of the Google Books OCR.