Split a stacked interest set into 5 — found the one carrying 80%

Split a stacked interest set into 5 — found the one carrying 80%

Had 5 interests crammed in one ad set, 1.6 ROAS, looked 'fine.' Broke each into its own set, $40/day:
— 4 of them: 0.9–1.3 ROAS, bleeders
— 1 of them: 3.4 ROAS, the whole engine

Killed the 4, poured budget into the winner. Set-level ROAS to 2.9 inside a week.

Stacked sets hide your real winner under dead weight. Unstack and stare.