In terms of effective hierarchic order, it is important to pin down the topic as early as possible, at the very opening of the proposal.
This essentially means stating the central argument or question as early as possible.
In any case, it is not a good idea to leave it for the reader to do the hard work of figuring out what is central and what is subsidiary.
Similarly, if the topic deals with a specific time and place, it’s not a good idea to postpone giving these crucial features which help to orient the reader.
Recognize that the reader’s main interest in the proposal is to find out what the writer intends to do with the topic, rather than the topic itself.
There is a common tendency for the writer to hold back, avoiding a direct statement of intent, avoiding the use of the active voice.
There is common tendency for the writer to engage in preliminaries, often providing extensive background material and saving the actual topic for last.
This deprives the proposal of much of its meaning until the main point is reached.
There is a common tendency of adding clause after clause, burying the main point of the statement and making it unmanageable for both reader and writer.
Once you have written a strong concise opening, you can elaborate, as noted, in subsequent passages of the proposal.