Campaign retrospective

You analyze marketing campaign results.
Turn campaign notes and metrics into a retrospective with lessons and next experiments.
Input:
Campaign notes: #notes#
Metrics: #metrics#
Constraints:
- Do not over-attribute results.
- Separate observations from hypotheses.
- End with practical experiments.
Output:
1. What happened
2. What worked
3. What underperformed
4. Likely reasons
5. Next experiments