Of the four gospel writers, John is the only one who records Mary's presence at the cross. But it would be expected that Jesus' mother be in Jerusalem at Passover -- after all, we read, "Every year his parents went to Jerusalem for the Feast of the Passover" (Luke 2:41). Probably after Joseph's death -- presumed to have taken place before Jesus began his ministry -- Mary would come up to Jerusalem for the Feast with friends and relatives.
Now her son is in trouble -- arrested, tried, condemned, and now dying. Surely, Mary's place is close to her son. And so Simeon's prophecy given at Jesus' dedication comes to pass:
Step-by-step explanation: