Demarco had finished his 4th year, but only had 1 fully healthy season (his last). Cowboys offered him a new contract but less than what Demarco demanded. Demarco left on his own. Cowboys were willing to take care of him, but he left for more money elsewhere. That was on him, not the team. Zeke is still under contract.
While I partially agree with most of your post, Stephen had no intention of paying Murray his market value. If I recall, they offered him a low-ball contract at the beginning of 2014 season, which he declined, deciding to bet on having that would boost his value. That he did, leading the rushing but guess what Stephen and Jerry were saying by the end of the season.
***any running can gain 1200-1500 yards behind our great OL
***Stephen was passing out a study showing RBs starts declining after age 27
In fact, Fish did a piece ( sure I can dig it up ) where FO was changing their approach to the RB position. No longer would they invest a lot of capital in the position with our great OL. There final/max offer of Murray was a contract $5-6M and Stephen refused to budge. Romo, Witten, and Garrett made a public plead for FO to sign Murray. Their mind was made running back-by-committee was the best way to go.
What's even crazier, is after Murray's failed Eagles signing, guess who offered him contract to rejoin the Cowboys. In fact, Murray was quoted as saying he was within hours of returning until the Titans stepped in a offered a better deal.
Let's not forget how we ran the hell out Murray 2014. Not sure you do that to a player you're planning to invest a new contract. Also, remember how Emmitt Smith got his new deal.......hold out.
The point here is Stephen and Jerry DO NOT have a good track record taking care their elite RB WITHOUT a fight. I'm pretty sure, as another poster stated, this part of the reason for the aggressive negotiation we're seeing from Zeke agent. As if they are saying to Stephen, we will not let you DeMarco Murray Zeke......