Tensions with the opinion shows were the breaking point for Smith, people familiar with his decision said.

Smith indicated that he has agreed to what is known as a "non-compete," a clause in a contract that ensures he won't immediately jump from one network to another.
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This means he will not be joining CNN, MSNBC or another network right away, despite rampant speculation in the news business that he might.

Such a departure, occurring suddenly on a Friday afternoon in the middle of an anchor's contract cycle, suggest a severe fissure between Smith and Fox management, though both sides spoke favorably of one another when announcing the exit.
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"It feels like death in the news division," a senior Fox employee told CNN about Smith's departure, saying staffers at the network were "shocked" and that some were crying. "At least we had him."
Smith was no exception to the feud between opinion and news. In late September, Tucker Carlson, a pro-Trump host, mocked Smith when he stood up for Judge Andrew Napolitano. Napolitano was called a "fool" by a guest on Carlson's show for saying Trump had committed a crime, and Smith had said the attack was "repugnant."

In his exit, Smith alluded to the tension between the opinion and news divisions, saying that the news division had always "endeavored to deliver" the news "while speaking truth to power, without fear or favor, in context and with perspective."