In his generally excellent commentary on Daniel, Dale Ralph Davis makes an odd comment. He's responding to the allegation that Daniel is a pseudonymous book written in the mid-2C BC, but set in the 6C BC. He says:
Why should they give solemn credence to "prophecies" they knew had been produced by a bunch of visionaries who were their own contemporaries? What divine authority could these pack? The Message of Daniel (IVP 2013), 20.
i) On the face of it, this comment is peculiar. Perhaps I don't know what he means. Or perhaps he didn't succeed in saying what he means.
Surely, many OT prophecies were produced by visionaries who were contemporaneous with their audience. And these had divine authority. They were sent by God to speak his words in his name.
ii) I'd add that in the course of church history, you have men and women who claim to be prophets, and their oracles are sometimes taken seriously, at least within their sect or cult or band of followers. But there's a catch. If they make false predictions, then they discredit themselves. Although some of their adherents follow them no matter what they say or do, although some of their adherents explain away the discrepancies, this produces a crisis of faith. Some, or many, former followers become disillusioned with the would-be prophet or prophetess. They drop out of the movement. Some of them write in opposition to their former sect or cult.
An analogous case is when a popular Bible teacher makes an end-of-the-world prediction based on his confident interpretation of Bible prophecies. He doesn't claim to be a prophet in his own right. But he does claim special insight into the meaning of Scripture. He was able to crack the code.
That happens every so often in modern times. And when his prediction fails, he loses credibility.
If Daniel was actually a contemporary of Jews during the Antiochean crisis, and he mispredicted the death of Antiochus, then we'd expect his oracles to suffer the same ignominious fate. At the very least, they'd be very controversial in Judaism. Hard to see how they could possibly attain canonical status.
So that's one reason, among others, why the liberal date for Daniel is implausible.