my suggestion for the final sum up would be the following:
- Repeat the objective, if possible quantifying it (eg “Dear Mr CEO, you asked us to understand whether we should buy company X to increase our revenues by Y in Z years”)
- Provide answer-first recommendation + motivation for that. (eg “After our initial analysis we would recommend not to buy the company. The reasons are that (i) there are not enough revenues that could be generated by current products and (ii) there are no new products that could be developed any time soon. In particular..”). There is no need to force the presence of three reasons here, unless you indeed have three reasons. If you have two strong points only, it’s ok to use two.
- Provide next steps. (eg. “In order to meet our goal, we would be happy to analyse further companies that could be interesting for us. In particular..”)
Given what you mentioned, it could be that:
- You did not clarify the objective at the beginning and the interviewer felt that led to a “too quick” jump to the conclusion
- The motivation in point 2 was not deep enough
Having said that, I agree the feedback is a bit strange, as an answer-first approach is the standard way to proceed for a final recommendation.
Hope this helps,