It often happens that the sway of evil makes a person commit great sins and then such people despair and this desperation makes them commit even greater sins because they think that they have crossed the point of no return so whether it be one sin or many it does not make a difference.
The intercession by the chosen ones gives them a sense of hope that if they should desist and reform then it is possible that the intercession by the pure souls may result in the forgiveness of their past sins. So the hope of salvation makes a person desist from sins, reform and return to piety.