Twenty years after the resurrection, the apostle Paul wrote a letter to the church at Corinth. In that letter, defending the resurrection as a verifiable historical event, he made a list of witnesses.
...He appeared to Cephas and then to the Twelve. After that, He appeared to more than five hundred brothers at once, most of whom are still living, though some have fallen asleep. Then He appeared to James, then to all the apostles. And last of all He appeared to me also, as to one of untimely birth.
1 Corinthians 15:5–8
Read it again. Paul is writing, around AD 55, a list his readers could verify. Most of whom are still living: the readers in Corinth could, if they wished, travel to Judea and interview some of those five hundred witnesses who were still alive.
Paul appeals here to living memory, to people his readers could still seek out and question.
The list grows to:
Cephas (Peter). The Twelve. More than five hundred brothers at once. James (the brother of Jesus, who had not believed before the resurrection). All the apostles. Paul himself.
Summing what is recorded between the Gospels and Paul's list: more than six hundred individual witnesses, distributed across at least seven distinct appearances, over forty days, in at least three different geographies.
This is what a real event leaves behind: a chain of people who saw it, each able to point to the next.