The Pharisees and Herodians were normally antagonistic towards one another but for different reasons they both wanted to trap Jesus. The Pharisees liked to parade their virtue but many of them were venal and harsh to those who they regarded as sinners. The Herodians, a political group who supported Herod and colluded with the Romans for reasons of convenience, were afraid Jesus would upset their comfortable lifestyle by provoking their imperial rulers. These had conquered Palestine and taxed their new subjects. Their legitimacy could indeed be questioned. On the other hand the gospels mention prominent Romans who paid far more attention to Jesus than his own people. The centurion whose servant he healed (Matt. 8:5-13), the centurion who proclaimed Jesus at the cross (Matt. 27:54) and the centurion Cornelius, whom Peter baptised (Acts 10), are good examples. Jesus was nearing the end of his life and it is likely that Matthew decided to take the opportunity to show that Jesus was not a revolutionary. Faced with the choice between supporting the tax, and therefore being disloyal to his own nation, or opposing it, bringing himself into conflict with the imperial authorities, Jesus responded with a clear outline of civic and religious duties.
He taught an important lesson, since there was - and still is - a tension between state and religious governance. It is vital that clear distinctions are made between the two. A theocratic government and a government that does not honour the faiths of its subjects are both unhealthy. Probably society works best when each monitors the other in a helpful manner. In the first reading Cyrus, King of Persia, seems to have done just that.