What factors led to the increasing popularity of the presidential system of government in West Africa?

The
increasing popularity of the presidential system of government in
Africa is due to the following reasons. 

• The presidential
  system has a fixed tenure of office for political
  holders and this ensures stability of executive and the political system in general.
•  Promptness
  of action and initiative in administration since the president has executive
  powers derived from the people and from parliament.
•  Selection
  of professional experts to ministerial departments based on
  merit and professional expertise and less of political
  considerations.
•  The
  system makes it possible for responsibility for what is done or left undone to be easily located in one man rather than a
  group of men for he can be seen receiving all the glory
  and the above on account of his work. 
• Decision
  are made faster because it is easier for a single man to make up his own decisions than a group of men.
•  It is easy
  to lay blames and hold a specific person responsible for what
  is done.
•  Since
  the executive is headed by a single person, all efforts are
  geared towards a common goal rather than plurality of goals. 
• It
  creates a more responsible and more dynamic leadership.
•  In
  addition, the system allows for division of labour which increases
  efficiency in the management of the affairs of the nation. 
• Enough time for the
  ministers because they have enough time to
  attend to their duties because they only belong to the executive
  arm of government. 
• It
  prevents unnecessary conflicts which often arise in a parliamentary
  system. In presidential system powers of head of government and head of state are fused and
  exercised by the executive president.
•  The
  desire by West African political leaders to experiment a new system led to
  the adoption of presidential system of government.