Because it is a term you have used previously and I don't know exactly who you are referring to.
Previously, I have almost always qualified the term with the adjective 'religious'; I assumed that by now most people would have understood that association, especially as it was these same people who are recorded as having requested the death penalty of the Roam authorities
So, they wanted rid of Jesus, hence they sought his execution, which seems reasonable - but having done so the matter would have been closed: the 'problem', such as it was, is resolved from the perspective of the religious leaders.
I would agree, if it had taken years for any 'resurrection'claim to have surfaced, but the fact that it surfaces at the very next religious festival - Shavuot - a mere 50 days later (hence the Jewish term Pentecost - '50th day') suggests that it hasn't gone away. Why else arrest the apostles and try to ban them from preaching and speaking about Jesus?
So, no contemporary details that are external to the much later NT.
"So, no contemporary details ..." can equally be laid against the vast majority of documentation from the period. And, of course, many of them give a Roman slant on the situation.