This is a parallel passage to what we see in Matthew 10 and Mark 6. Yeshua calls the twelve together and gave them specific power over demons and power to heal. This was a specific gift to His twelve disciples. Paul, as an apparent replacement for Judas, was given these same gifts.
The chief priests and elders took counsel against Yeshua. Apparently they found Him guilty, even though He was innocent of any evil. But this was necessary in order for prophecy to be fulfilled.
When the Pharisees heard that Yeshua was casting out demons, the claimed He was doing this by the power of Beelzebub. Now the Pharisees want a sign “from heaven.” They wrongly reasoned that some miracles here on earth could come from Beelzebub. They thought that if they saw a sign from heaven, then they could determine if Yeshua is really a prophet from Elohim or not. Yeshua showed signs before, why would He not show a sign for the Pharisees? Yeshua did not want them to heed His warnings. He already said they were not to understand His message and that is why He spoke in parables (Matt. 13:9-15).
John was in a tough situation. He was imprisoned because he condemned the actions of Herod (Matt. 14:3-4). He was understandably confused and distraught. He knew that he was the one announcing the arrival of Messiah and that Yeshua was to set up the Kingdom. But if that is the case, then why was he (John) in prison??