Kyler has WAY more value than a 2nd round pick. All of the dead cap money is tied to the Cards, not the team that trades for him.
Even with the Cardinals eating the remainder of Murray's pro-rated signing bonus, a team trading for him would still be on the hook for salaries of $37M, $18M, $23M, $19.5M, and $34M in 2024-2028, PLUS bonuses of $850K per game ($14.5M per year if he actually plays 17 games) for the rest of his career. A total of over $40M in his first year with the new team and an average of over $40M per year for the duration of the contract.
That's no longer top 10 QB money, but if he's playing badly enough for the Cardinals to jettison him and take the massive cap hit, it's hard to imagine another team trading much for him, knowing they'll have to pay him that much.