That is an interesting question, but I am not sure I fully understand it. Gain popularity were? In Mexico? in the US? in Academia?

Broadly speaking, the 1880s had the establishment of a robust Liberal state (nicknamed the "Porfiriato") that expanded education and reformed the historical pantheon of Mexican Independence. As for the 1940s, that is when the Mexican Revolution (1910-1930s) culminated, and perhaps that spike in popularity that you notice there is related to the post-Revolutionary moment.

Hope this helps, and maybe if you can refine your question I can try providing a more thorough answer.