The strategic location of the byzantine empire allowed control of the key trade routes between the

The answer is - between Europe, Africa and Asia.

The Byzantine Empire had a territory that was spreading on parts of this three continents, more specifically, it had parts of the edges of this three continents which were trading roots both on land and on sea for centuries before. So the Byzantine Empire took advantage of it and grew enormously in power and wealth because it had control over these trading roots.