Around AD 70, there were over 20,000+ people who had witnessed at least some of Jesus’s life and ministry.
This is relevant because they would have been quite accessible (e.g. Jesus ordered his disciples/witnesses to be testifying of his words and deeds.)
Quadratus of Athens, who died in AD 129, recalls witnesses of Jesus being loud and present in the Mediterranean area, and he would have been referring to the time around AD 80.
In the Gospel of John there are indications that the author was a disciple of Jesus and had survived until the end of the century.
This is relevant because the Gospel of John was written around AD 80-90, and therefore he and his apparently loud teachings (with followers) was all the more available in AD 30-70.
In AD 30-70 Christendom, witnesses of Jesus’s life and teachings actively recounting and spreading what they heard and saw.
This page analyzes 5 arguments
This of course helps show that accessible known witnesses were available during these later decades because you can't be actively relaying testimony unless you are alive and available.