I guess that just depends on what you mean by them being confident. How do you see these that you mentioned as different from, say, David?
Much love!
None of them were weak as they never complained. David, however, was afraid, so afraid that he had to lie about it. He even put on an act of being a madman, drooling all over himself to keep from being killed by the king. In reading the Pslams, we don't see David being consistently strong and unafraid. He is up and down . . . back and forth. David struggled mightily as did the Apostle Paul, with much crying and despair.
Caleb and Joshua, however, were the only two from the original group who left Egypt, who were allowed to cross the Jordan and set foot on the Promised Holy Land, because they served the Lord "Wholeheartedly." It was Joshua and Caleb, who in their 80's, wanted to fight the Giants found after their reconnaissance mission. The other ten who went with Joshua and Caleb lied about taking over the land, which upset them both, for they trusted God that He would give these Giants into their hands.
Confidence is from the Lord? That's such a weird thing to say when the primary emotion of the Bible is dealing with the instilled fear, shame, and guilt that stems from the Law of Sin and Death. Therefore, fear is the dominant emotion of the Bible . . . and that isn't good, especially if "Confidence comes from the Lord!"