Too explosive to be elite. You will never be an A-level fighter with an NFL-level gas tank.
Also, he was fighting Matt Brown. A born fighter who can beat well trained 'athletes' via pure natural talent. No matter what Silva did, it would be almost impossible for him to finish a guy like Brown. Same reason a jacked up, well trained athlete like Overeem will never be in the same league as a natural born fighter like Cain Velasquez.
And it's the same reason a guy like Bob Sapp can play professionally in the NFL and look like a joke when it comes to fighting.
Silva does deserve respect for hanging in there as long as he did though.