This is a peculiar verse in a peculiar place. It doesn’t seem to fit, and no time is spent explaining it. If you accept that verses 13-19 were a later interpolation, then it makes a little more sense in the context of the story in verses 7-12. There is also a bit of phrase that sometimes ends up here and sometimes at the end of verse 19, where it makes zero sense: “And they went into a house.”
In the story from verses 7-12, Jesus Physician is trying to escape the crowds at the seashore but is met with more crowds. With this verse, they try to escape into a house, but the crowds again follow them so they are unable to eat.
During the siege of Jerusalem, the city was overcrowded and its people were starving. Here, Jesus and his people are in a house so crowded they cannot eat. It’s difficult to not see a connection.