Also, the quintessential factor exacerbating these 'worldy destructive' tendancies, is the Starforge.
The Starforge is almost like a living being - feeding and hungering for Dark Side energies. Malak, of course, was not mentally of sufficent strengh to resist the corrupting effects of the Starforge. And the more Dark Side energy the Starforge consumes, the more it needs, thus requiring greater & greater wanton destruction in order to satisfy its insatiable appetite. This explains why Malak became increasingly evil and destructive, bordering insanity.
But now that it's established that Malak (and not Saul), was the chief instigator for the bombardment of Telos & Taris, the question still remains concerning Dantooine...for if Malak was aware of it before, why was no action taken until Saul Karath's? And at that rate, why wasn't Dantooine common knowledge for Saul in the first place?