"Let Christ the King of Israel descend now from the cross, that we may see and believe. And they that were crucified with him reviled him." (Mark 15: 32)
The Pharisees, religious leaders, and scribes wanted Jesus to prove His royalty by coming down from the Cross.
He could not come down from the Cross, because if He did, then we would all still be dead in our sins:
"For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;" (1 Corinthians 15: 3)
If He had not died on the Cross, then He would not be our propitiation now and forever:
"1My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous: 2And he is the propitiation for our sins: and not for ours only, but also for the sins of the whole world." (1 John 2: 1-2)
He was King at His birth, anyway:
"Saying, Where is he that is born King of the Jews? for we have seen his star in the east, and are come to worship him." (Matthew 2: 2)
"11And Jesus stood before the governor: and the governor asked him, saying, Art thou the King of the Jews? And Jesus said unto him, Thou sayest." (Matthew 27: 11)
Yet when He came bearing the Good News, the religious leaders of His day rejected Him. Not because they doubted His power, but rather because they feared losing their power:
"22Then was brought unto him one possessed with a devil, blind, and dumb: and he healed him, insomuch that the blind and dumb both spake and saw. 23And all the people were amazed, and said, Is not this the son of David? 24But when the Pharisees heard it, they said, This fellow doth not cast out devils, but by Beelzebub the prince of the devils." (Matthew 12: 22-24)
"31Wherefore I say unto you, All manner of sin and blasphemy shall be forgiven unto men: but the blasphemy against the Holy Ghost shall not be forgiven unto men. 32And whosoever speaketh a word against the Son of man, it shall be forgiven him: but whosoever speaketh against the Holy Ghost, it shall not be forgiven him, neither in this world, neither in the world to come." (Matthew 12: 31-32)
The Gospel of John affirms the envy of the religious leaders:
"47Then gathered the chief priests and the Pharisees a council, and said, What do we? for this man doeth many miracles. 48If we let him thus alone, all men will believe on him: and the Romans shall come and take away both our place and nation. 49And one of them, named Caiaphas, being the high priest that same year, said unto them, Ye know nothing at all, 50Nor consider that it is expedient for us, that one man should die for the people, and that the whole nation perish not. 51And this spake he not of himself: but being high priest that year, he prophesied that Jesus should die for that nation; " (John 11:47-51)
Even though Jesus fulfilled every prophesy, and even after Jesus rose from the dead, there were those who doubted:
"And when they saw him, they worshipped him: but some doubted." (Matthew 28: 17)
Jesus related this sad development earlier in His earthly ministry:
"And he said unto him, If they hear not Moses and the prophets, neither will they be persuaded, though one rose from the dead." (Luke 16: 31)
During His ministry on the Road to Emmaus, Jesus revealed Himself in His Word, and only when the two traveling with Him believed what He said, then they saw Him.
With Jesus, believing is seeing, because if we do not believe that He has taken care of all things, al our sins paid for all prophesies fulfilled in Himself, then we will not able to see Him as He is, or His blessings.