Palpatine's behavior in ROTS is run of the mill madman behavior. Compared to the more outlandish villains like Blofeld in the James Bond movies, Palpatine doesn't seem so insane.
As for how a Sith focuses himself, that would not be too hard if he's actively fighting with another person. Also, since Sith usually fight Jedi, and Jedi and Sith have been ancient enemies for thousands of years, why not have burning rage towards Jedi? Obviously, Palpatine derives a thrill from laughing insanely in combat and using the force in the most twisted ways possible.
Sith Focus Methods and Giggling Palpatine
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