Zinedine Zidane's Real Madrid had plenty of success in a 4-3-3, too.
The main strength of a 4-3-3 is the presence of a third player in central midfield, which creates a numerical overload when up against a team playing with two. This helps in build-up, playing through the lines, creating chances and overall domination of possession. The basic shape of a 4-3-3 tends to create more triangles between players, and so more passing lanes are open to the ball-carrier. This, in theory at least, makes it easier to play a possession-based game – and this is one reason Johan Cruyff preferred such a shape for the positional game he liked his teams to play. Zinedine Zidane's Real Madrid had plenty of success in a 4-3-3, too.