Its mainly because Hotstar touches all fields that an online platform could bring. Sports,movies,foreign contents, live tv with popular news channels,serials,web series etc. Obviously the major crowdpuller is IPL. Many women regularly use hotstar to watch their serials now a days(regions where Star is dominant) and like others Star channels is not available outside hotstar(except tatasky). Simultaneously Hotstar is able to compete with Amazon-netflix and Voot-Sonyliv-zee5-sunnxt. But I can't believe that it overtaken YouTube.