Nassar's biggest mistake was not staying at that weight. he looks incredible there. He tried to be too much of a mass monster and it didn't work out well. Looking like that photo of just great symmetry is unmatched. He could have easily won a couple olympias like that.
Not with the IFBB politics
He actually grew about 10-15 lbs in some of his later shows and still placed well. I think he was 275 at the 96 Olympia (the show where these pics are taken), and still won the Arnold Classic at 289, 3rd at the 98 Olympia at 280, and 2nd at 97-98 Arnold Classic at 285.
His placings began to drop not due to chasing more size but after his divorce with his former wife, as in the immediate term it had a huge emotional toll on him and he began to lose motivation and get fed up with the unfair judging decisions. Lots of people actually underestimate the importance of having someone supportive to prepare your meals and help you during your contest prep. Even guys who were single like Kevin Levrone would hire someone to prepare their meals for them.