Technology

Well, define "long after". The earliest surviving non-Christian source is Tacitus who is generally considered to be a reliable histographer and had access to records that are now lost, he wrote, in about 116 CE, in the context of Nero's burning of Rome (64 CE):

Christus, from whom the name had its origin, suffered the extreme penalty during the reign of Tiberius at the hands of one of our procurators, Pontius Pilatus, and a most mischievous superstition, thus checked for the moment, again broke out not only in Judæa, the first source of the evil, but even in Rome, where all things hideous and shameful from every part of the world find their centre and become popular.

116 CE should be about 80 years after crucifixion, not that long. If the Romans had not done it they would have considered themselves slandered and mentioned it in their justifications as to why Christianity should be persecuted, it would have been part of the contemporary political consciousness.