"Idiot" is an interesting word to use about the guy who outwitted the FBI, NPA, L, Mello, and nearly killed Near. He is arrogant, yes, but he knows how to keep his ego in check after L's Lind L. Taylor trap(think of Part 3 DIO learning from his blunders in Part 1). This is the same dude who found a way to dismantle the FBI and NPA's trust in L, found a way to kill while being observed by 64 cameras, trick a FBI agent into killing his own allies, decieved a detective into giving their real identity (twice), removed all suspicions of him being Kira by removing his memories and establishing a fake 13 day-rule while also creating a 3rd Kira to misdirect the task force, and lastly manipulated a shinigami into killing themselves to kill his rival. That's an "idiot"? I don't see how Columbo will do better than L did, who, aside from having absurd feats (just look at L's profile), also had a way more secure identity than Columbo. L also already tried the same tactics Columbo does, with how often he tried to catch Light off-guard and feed his ego, yet still failed (pretending to be his "friend", the letter trap in the cafe, bluffing about adding more investigators, and his face reveal in the university). Even if Columbo suspects Light is Kira, finding proof is nigh-impossible, which is the reason why L lost in the first place. While I think Columbo and Light are likely even in intelligence, Light has already dealt with the stick throughout the course of his story. You know it's bad when not even locking up Light and torturing the 2nd Kira was enough to prove he was Kira.