Upvote:0
Jesus provided an answer to this question at the end of the parable of the rich man and Lazarus:
And he said unto him, If they hear not Moses and the prophets, neither will they be persuaded, though one rose from the dead. (Luke 16:31)
The religious leaders of the day had departed from the teachings of Moses and the prophets (e.g. see Matt. 23:2-3); the praise of the world mattered more to them than doing the will of God (see Matt. 23:23-25). If Jesus' message were true, it undermined the things they cared about (money, power, etc.), so they preferred to believe it was not true.
Similar sentiments are sometimes found in skeptical circles today. Some so desperately wish for God not to exist or for sexual immorality not to be sinful, that no amount of evidence will convince them to believe something they do not want to be true. It is tragic when people spin in circles around moral arguments for God's existence (example), preferring not to condemn even atrocious violence as wrong because, in doing so, they acknowledge that right & wrong exist.
Upvote:2
OP: "if given clear testimony from the best of the Roman guard that the guy fulfilled his own prediction and was raised from the dead by supernatural forces,"
There's a bit of background that might help. The Sanhedrin generally and the chief priests specifically didn't see it themselves. They can't really rely on the testimony of the unclean guards. And they could interpret that some guards did not report the same thing; some left; only some said "wow" (Mt. 28:11).
At the same time, the elders also must have realized that Daniel's 70 weeks of 7 had been fulfilled. And as the OP said, Jesus had told them He will resurrect on the third day. What did all this mean to their position, their pocketbooks, their piety?
Tell everyone the body was stolen. (this later has morphed into the swoon theory that Christ only appeared to die on the cross, but was resuscitated in the cool tomb)
So, to answer the OP, it either wasn't clear to the elders that Christ had risen from the dead per partial testimony from the unclean Roman guards or if it was clear, they clearly would have understood what that meant for them.