It's common that much academic research is originated in academic environments in which English is not necessarily the language generally spoken, situation that it may occur, for instance, in many non-English speaking countries.
Between the advantages in using the local language for research is that it permits their access (reading, comments, feedback, etc.) by local experts in their own idiom, which would be difficult if the paper had been published only in English, and additionally, if many local experts are not comfortable handling foreign languages.
On the other hand, the benefit of publishing research in English is that it allow their access to broader international research communities who might provide valuable insights to be considered for future research.