We brought back the guy that got drunk and killed his team mate.
That's among several reservations. They brought back (or brought in), players like Brent, Hardy, etc. The team took all the backlash, PR hits in the press, etc...and none of it translated to wins. To Jerry's credit, he believes in second chances...but unfortunately it hasn't worked out in several instances.
Everyone makes mistakes. Tom Landry had his share of problem players. And there were some big problems in the 90's. Michael Irvin being one of them. Charles Haley another. But football mattered a lot to those guys. Does it to Manziel? Michael Irvin was the heart & soul of the team. No one practiced harder. He partied like nobodies business...but few were more dedicated to their craft or their teammates. Manziel unfortunately has proven otherwise so far...to include blatantly lying to his coaches and management, essentially abandoning his teammates, missing appointments with trainers, etc. And that's not taking into account whether his game translates long-term to the NFL. Additionally, the temptation & scrutiny will only be magnified if he comes to Texas (his old stomping grounds).
As I've mentioned previously...if trading for a QB still under his rookie contract, I'd Mike Glennon. The only things more favorable in Manziel's case to date, is that he has another year remaining on his rookie deal & is younger.