Auction overlap happens when two of your own Meta ad sets target overlapping audiences and end up competing against each other in the same auction. Meta suppresses one to avoid self-competition, which wastes learning and can raise costs.
Why running five campaigns can hurt
When your ad sets chase the same people, Meta will not bid against you twice; it picks one and holds the others back. The result is fragmented conversion signal, each ad set starved of the volume it needs to exit the learning phase, and often higher costs. More campaigns is not more reach when they fish the same pond.
The fix is consolidation
Fewer, broader ad sets under campaign budget optimization usually beat many narrow overlapping ones. You can check the audience overlap tool before launching, and consolidate when you see the same audience split across ad sets. One campaign that clears the learning threshold beats five that never do.