To understand the weight of an "ISM Malayalam fonts zip" file, one must look back at the dawn of Indian language computing. In the 1980s and 90s, computers were predominantly designed for the English language. The ASCII (American Standard Code for Information Interchange) character set had no room for the complex, curvilinear glyphs of Malayalam.
A comprehensive font pack usually includes a mix of traditional and modern styles: ISM - C-DAC ism malayalam fonts zip