Your argument continues to be based on a technicality because UA/CO merged before AA/US. It's like saying DL was the largest airline before UA/CO and then AA/US merged, and now they must be shrinking because they're #2. Even when combining all carriers, neither the combined AA or UA is a clear #1 in the 2010-2011 timeframe. They wobble back and forth.

UA was a strong #2 at LAX before Jeff set foot on the property (2009). They're a strong #3 today. Their LAX traffic has been remained remarkably steady for more than a decade. The narrative that they're shrinking and collapsing because of Jeff simply isn't true. Their fall from #1 due to a growing AA happened well before Jeff was in the picture.