But does it mean the unfinished vilain is to be an idiot ?
How does him getting mad make him an idiot? Immature yes but idiotic? No. The Dark Side feeds on passionate emotions like anger, hatred and fear and since Kylo hasn’t completed his training yet he hasn’t mastered the subtleties of keeping his anger in check so it can be used as a time that would benefit him the most.
And why would Snoke choose leaders that are so incompetent ? Tarkin and Vader were assholes but efficient and competent assholes. They ultimately fail because of unpredictable bad luck (a gifted pilot out of nowhere - a simple farmer when the movie begins - who got help by an old wise man - presumed dead when the story begins - and by a smuggler who decided to take side for the first time of his life: what are the odds ?).
Technically had Vader gotten the information on where the Rebel Base earlier in the film Yavin IV would have been destroyed. At least Kylo was successful in one of his mind probing scenes. As it pertains to Hux he did fail at getting the droid but it was his idea that the Hosnian System would be destroyed and not Snoke’s. And unlike Tarkin, General Hux had the smarts to get out of dodge before Starkiller blew up. Also shouldn’t have Vader sensed Han and Chewie coming?