I don't claim to be an expert on the inner workings of airlines, but I manage a few networks of passenger buses. Every time we add capacity, we attract more passengers, without fail. However, after a significant increase in capacity, our KPIs for that year take a blow. Two of the main measures are passengers per service kilometre, and revenue versus expenditure by route - both of these drop instantly after a capacity increase, then usually take some time to increase to the levels experienced prior to the capacity increase, and eventually exceed that. It is difficult to tell how long it will take before the capacity increase will yield growth.
If things are a bit shaky with shareholders, there's an argument for ensuring that the balance sheet shows a firm profit, which equals a bad time for absorbing a few negative KPIs with view to long term growth. Erring on the side of caution for a while and choosing to sit tight until the time is right might be the strategy.
Nevertheless, increasing capacity is really the only way to continue to grow the business in the long term. I guess a lot comes down to timing.