Why did the women come to anoint Jesus AFTER He had been buried?

Ancient Hebrew burial practices included anointing the body with spices. This was likely to help with the body’s smell of decay as the Hebrews did not practice embalming (as seen in John 11:39 with the death of Lazarus whom his sisters believed would smell after four days in a tomb). 

Nicodemus and Joseph of Arimathea anointed Jesus as they buried him (John 19:38-40) but likely would have been rushed in their efforts to finish before the Sabbath began. 

The women who had followed Jesus so faithfully seemed to have seen Jesus’ burial and may have wanted to make sure the anointing was done without rush as well as have an opportunity to pay their own respects. So they began preparing spices, but by the time they were done it was the Sabbath. So on the third day they came with anointing oils and spices (Luke 23:55-56) (Source 1, Source 2).