At least the disciples were consistent; every one of them reacted the same way. We are in good company. They just acted like human beings who do not believe the truth.
There is a difference between the desire to believe and actually believing so that it becomes a part of one's life. The Jews have a zeal for God, but not according to knowledge (Romans 10:2). Paul implies it is not according to truth.
Human beings operate from a mind that has a natural bent away from God. It is something that is inherent within us - we have been pre-programmed away from God by the time God begins to work His miracle in us. We consistently want to go our own way in disbelief. One can imagine where this leads. We have to recognize that there exists within us a sincere desire to do what is right, yet we must make conscious effort to choose the right. That is what builds character.
God works us into a position where we are free to make the choice in a way that others, who do not have the truth revealed to them, are not free. He has removed the scales from our eyes, but it is not a one-time thing or done all at once. Rather, it is something that progresses - each one of us at a different rate, at the rate we are capable of using it. However, He always puts us in a position where we have to make a conscious choice. Otherwise, we are not living by faith, and character will not be built.
We can see that God leads us to a point where the mind is open or receptive to the truth, but we have to use the truth to ensure that we move in the direction He wants us to go in.