This quote here said it all:

"It is not a good sign when the judge you’re arguing before has to actively remind you that you’re supposed to be arguing for consumers, not one specific company, Sony."

That was the problem right there.

Everything the FTC did in this case, and everything the FTC argued for, was about how bad the merger was going to make things for Sony.

Consumers weren't mentioned.

Benefits accruing to consumers were explored, or if they were, were not elucidated on.

It was all Sony, all the time.

Source: Three strikes for the FTC