What Palpatine/Sidious did in the PT was "disguise" his true self and motives from the Jedi,who by the way had their hands pretty full with the Clone wars,even with that in AOTC I believe Yoda felt an uneasiness with the chancellor,and in ROTS before Anakin tells Mace that Palpatine WAS a Sith Lord,Mace said "the dark side of the force surrounds the chancellor." The dark side's power gives different abilities than the light side...ex. Force Lightning and in the case of sith lord Sidious,powerful mind manipulation.