Completely disagree with the order tbh. The only two with a case for being worse than Kumble are Vettori and Malik. Vaughan is one of the best captains this century, Gayle seems to be the most inspirational man under the sun. Ponting isn't great, but he's still a massively successful captain and his tactics are certainly in advance of Kumble. Vettori has a thankless job, being in charge of an exceptionally weak team and following one of the best captains ever. Still, i struggle to remember many mistakes he's made in his captaincy- barely an out-of-place fielder, bad toss decision or dodgy bowling change.
Malik, i've seen very little of (as has the cricketing world) so i can't really comment on.
It's not about Kumble's confidence going, his actual decisions have often been bad. Just off the top of my head:
Failing to employ a leg-slip to Clarke in Australia to the spinners, despite Clarke's repeated walk across his stumps. Two edges in the air in that region later, he shut the horse's door.
Batting on the greenest of green pitches against South Africa in the second test.
Sending in Ishant Sharma as a night watchman in the third test of the series just passed.
What really damns him, though, is how infinitely the better the team is with Dhoni in charge. It's not just that Dhoni gets the best out of players, his tactics are often much better too- more positive, but he knows when to defend and he knows how to do it, he usually makes the right bowling changes- Sehwag in the SA third test, for example. Kumble, as legendary a player as he is, was just not born to captain IMO.