go down, drop, etc. like ninepins
ˌgo down, ˌdrop, etc. like ˈninepins(informal)
1 (of large numbers of people) become ill/sick, be killed or die at the same time: In last year’s flu epidemic both children and teachers at this school were going down like ninepins. ♢ As the enemy advanced, men and horses went down like ninepins.
2 (of businesses, etc.) fail, go out of business, etc: Small businesses are going down like ninepins at the moment.
In the game of ninepins, you roll a ball towards a group of nine wooden objects (= skittles) in order to knock down as many of them as possible.