Why was John the Baptist imprisoned?
From these references, the simple conclusion would be that Herod did not like being reproved for his adulterous affair, nor, as Luke tells us for his being reproved for other unspecified aspects of his behavior. Undoubtedly Herodias’ influence helped to get John into prison as well. This is strongly suggested by what Mark tells us of her feelings towards John. People, especially wicked rulers, do not like being reproved.