Just as when people sleep and do not know what is happening, so the people of this world do not know that Christ will return. (See: [[rc://en/ta/man/jit/figs-metaphor]])
Paul is stating that it is at night when people become drunk, so when people are unaware of Christ's return they do not live a self-controlled life. (See: [[rc://en/ta/man/jit/figs-metaphor]])