Secondary succession usually occurs faster than primary succession because the substrate is already present.
In primary succession, there is no soil and it needs to form. This process takes time, as pioneer species must colonize the area, they must die, and as this happens over and over again, soil forms.
Secondary succession happens after some sort of disturbance. Vegetation has already been present in the area, but it no longer exists. Compared to the image below, secondary succession does not need to have pioneer species colonize the land nor does decomposition need to occur to create a layer of topsoil. These processes already happened.