Of course they were smart enough not to make a factual claim like Murray was intentionally getting people killed. They were able to convey the same message using jokes and a few cherry picked facts, and thus be immune to defamation suits.
With jokes like "looks like a geriatric Dr. Evil", "appears to be on the side of black lung", and "[his political activity is] the equivalent of watching My Girl and rooting for the bees" they suggested that Murray was evil without making any actionable claims.
And in their show after the case was dismissed, they embraced the "who in his right mind would take [this] seriously" defense wholeheartedly: accusing Murray of things like being Epstein's prison guard.
Factual (even if obviously untrue), but not defamation because, much as the court wrote in the case against Tucker Carlson (and before that, a similar case against Rachel Maddow): “the statements are rhetorical hyperbole and opinion commentary intended to frame a political debate, and, as such, are not actionable as defamation”