According to Shady Music Facts These were the most illegally downloaded albums of 2015 with over 20 million illegal downloads each Adele "25" Justin Bieber "Purpose" The Weeknd "Beauty Behind The Madness" Madonna "Rebel Heart"
I think it shows that Madonna still has huge interest but people no longer feel they need to go and buy a physical copy and will spend their money on a 'new' artist. However, it could mean people didn't warm to the tracks enough to buy it. Still, she's still up there!