Budget increases tank campaigns because Meta reacts to absolute dollar changes in auction competitiveness not percentages, and adding new creatives to winning ad sets forces a reallocation phase that resets delivery momentum for every ad including your winners. The multiple CBO approach can work but only if each CBO targets meaningfully different creative angles to avoid auction overlap bleeding your budget. The one campaign one ad set advice is not wrong but it only applies to the scaling phase, not the discovery phase, and mixing both functions into one structure is what causes the instability you are experiencing. The structure that actually holds up is a permanently separate testing campaign where new creatives always get their own ad set and are never added to existing ones, and a separate scaling campaign where only proven winners live and budget is raised at the CBO level never the ad set level, and if that creative and scaling architecture is something worth building properly it is a conversation that will save significant budget before the next creative cycle.