the top-down way of communicating is also sometimes refered to as the "Pyramid Principle". It emerges on the grounds of the mantra: "Think about your audience, first!" The canonical book on this was written by McKinsey's Barbara Minto: https://www.amazon.de/Pyramid-Principle-Writing-Thinking-Financial/dp/0273710516
As a consultant, you’ll be presenting your findings to busy C-level executives. In your interview you’ll be dealing with consulting Partners, who work everyday with CEOs and share their manners and approach. Hence, often the most challenging constraint you’ll face is time. What they expect from you is a short and clear main message or recommendation. Then, if they are interested, they’ll ask for details. This is called “top-down” communication.
It follows the principle that ideas should always form a pyramid under a single thought. The single thought is the answer to the executive’s question. Underneath the single thought, you are supposed to group and summarize the next level of supporting ideas and arguments. Then, for each supporting idea or argument, break that further into more ideas or arguments until you have formed a pyramid. Ideas at any level in the pyramid must always be summaries of the ideas grouped below them.
When comunicating your "pyramid", you should first lay out all elements of the upper levels before diving deep. For example, if the peak of your pyramig disaggregates into 3 buckets on the first level, list the three elements first before deep diving into any of them.