Southwest Airlines saw a chance in short distance flight that their competitors where ignoring. Everybody else was flying between small and large airports, (hub-and-spoke) while Southwest flew point to point, much like greyhound buses. So Southwest created a clear objective to be a substitute for greyhound buses but a faster and more convenient way to get around. 

This objective helped them slim their business to be more effective and efficient. For example, they only needed one type of aircraft which simplified training, rutin and maintenance. And considering it was short flights, no meals were served. This and much more “small corrections” created substantially lower costs than other commercial carriers and so they could offer lower prices. 

One reason the other airplane companies missed this because they hadn’t been specific with their goals. They were only comparing objectives to their competitors and not focusing on their own game or possibilities. Once the other airplane carriers caught on to Southwest, they were already too far behind and had no chance to compete in this new market.