IMO, no matter what Brady or the Pats did or said right after the Colts game would not have made a difference. From what I have read and concluded (other opinions may differ), a large majority of the owners wanted the Pats to pay a severe penalty for what they felt was too light a punishment for Spygate in addition to a slew of other potential infractions. In essence, the rest of the league wanted their pound of flesh. Oddly enough, I don't blame Goodell, as he was only doing what he was told.
The Wells report and investigation told the narrative that the league wanted as an outcome. They basically came to a conclusion and reverse engineered the report. They wanted the Patriots to burn and they burned them. In the Steelers case, there apparently is no outcry or long history of other teams complaining about them, so in their case the league swept things under the rug.
Not a surprise, as we all know the league has issues with consistency and at times makes things up as they go along. They could very easily have done the same thing with NE (the footballs were found to be compliant, nothing to see here) if they were interested in making the issue go away.
And to clarify, I am not suggesting the Patriots didn't do anything, only that the way the league proceeded they seemed pretty hell bent on punishing the Patriots.