If Jesus had been an eternal being at the time, or God at the time, what you say would be completely correct.
But suppose he was not an eternal being at the time. Suppose he was not GOD at the time but simply human. He might believe that he will be raised from the dead, might believe it very strongly, but still, as a human, the pain would still be real and there would still be doubts.
Where I do agree with you is that the fact of Crucifixion itself is not very inspiring and those who concentrate on that aspect miss the message of Christianity. There were at least two others who suffered the same way that very day, that very location, that very moment. It's likely that hundreds or thousands of others were crucified that same day across the Roman Empire.
The message of Christianity is Jesus life. GOD became man, and as man, walked among us, laughed, cried, ate, slept, danced, drank, shared and taught. He lived with us, he died, and he was raised from the dead by GOD and forty days later he ascended into heaven.
Aslan is not a Tame Lion