Have you seen Ronaldo,Messi, Ronaldinho, Ronaldo Nazario play
They are quick with their feet, critically quicker than their opponents in straighline speed, and quicker in changing directions- if you need a cosual demo of this watch messi highlights.
Moving quickly with your body allows to move the ball quicker than your opponent.
Also, if you’re faster than the defensive line, you can be onside and be able to poach balls with headers by running faster into good positions, and /or Jumping higher than the defender a la Ronaldo.
As said, a lot of game intelligence and skills have to be allied with explosiveness to be great. Not all great players are that much explosive relative to their peers, and not all pacey players are great players.