I was very surprised that the Jets got the return they did.
Maybe I'm putting too much into Miami getting only a 4th for Tannehill?
I believe you are putting too much into it.
Darnold is younger now than Tannehill was when he first entered the league as a rookie. And Tannehill was quickly closing in on 31 years of age when MIA traded him.
The age difference combined with 6 seasons of marginal play from Tannehill despite having a couple seasons with some decent talent around him combined with his contract are the biggest reasons he didn’t fetch much in return.
Darnold‘s only 23. Only has 3 seasons of tape, largely with poor talent/coaching around him and is still on his rookie contract.
He should be worth more than Tannehill was at the time he was traded.