In their Gospels, written fifty years after the facts, Matthew and Luke wrote that a Cyrenian named Simon helped Jesus carry its cross. Mark, who was a witness to the Way of the Cross, told us that Simon was the father of Rufus and Alexander (whom his readers knew well.)
Matthew, Luke and John each told us his reason for writing Gospel, like, Matthew wanted to show us that rather than abandoning the Law and the Prophets, Jesus came to fulfill them.
Critics had been saying that Jesus could not have been the Messiah because he suffered a sad death. Answering them, Mark composed his first eight chapters showing that Jesus, by his miracles and fulfilled prophesies demonstrated himself to be the Savior.
Mark concluded the first half of his thesis by quoting Peter as saying, "You are the Messiah." In the next verse, Mark launched into the second half of his thesis by "teaching them that the Son of Man must suffer greatly."