What does Mark 8:9 mean?

Mark says, "about four thousand people" while Matthew 15:38 says, "Those who ate were four thousand men, besides women and children." Since they are in the wilderness in the region known as the Decapolis (Mark 7:31), on the eastern side of the Sea of Galilee, scholars presume that the crowd is a mix of Jews and Gentiles.

The people have been there for three days, receiving healing and giving God glory (Matthew 15:29–31). This is not the first time Jesus has dismissed such a crowd, but the circumstances are very different.

After Jesus fed the five thousand-plus outside of Bethsaida, He immediately made the Twelve return to the boat and make their way home (Mark 6:45). He then dealt with the crowd on His own. The mostly-Jewish crowd had realized that He was the prophet promised by the Old Testament, and they had resolved to make Him king (John 6:14–15). Jesus apparently didn't want the Twelve infected with their nationalistic fervor. Soon, Peter will affirm that Jesus is the Christ (Mark 8:29), but, like with the demons (Mark 1:34), Jesus will forbid him from spreading the news (Mark 8:30). It's not that Peter is wrong, it's that he doesn't understand what Jesus as the Messiah has come to do. In practically the next breath, Peter will rebuke Jesus, denying that the King of the Jews must be rejected by the Sanhedrin and killed (Mark 8:31–32). It is not until after the resurrection that Jesus commands the disciples to spread the news of who Jesus is (Matthew 28:16–20).

In this case, however, in a mixed crowd of Jews and Gentiles, there appears to be no danger of rebellion against the Roman Empire. Bellies filled, illness and injuries healed, Jesus merely sends the crowd home.