It's far too early to tell anything about how the song is going to hold up, so I don't know why you are all rejoicing. It's rolling its early sales, of course it's dropping.
Fun. is selling 350k weekly, so 50k daily
so 1 day with 60% lead could be 100-120k
But you ought to consider fun. didn't lost #1 exposure last week but this week and that sales are always low on weekdays (right?) so I think 100K was very rational yesterday.
It's not actually decreasing faster, but fun.'s percentage gains are going to continue to get bigger and bigger for the same reasons I posted yesterday, unless it stabilizes.
I expected a way bigger drop overnight! It's holding up fine 
these months are gonna be really boring 