I wouldn't characterize checking the airplanes after one failed in flight as "proactive"..."proactive" would have meant finding the crack before the fuselage failed...this isn't the first time that fatigue has lead to failure, in the 737, or in several other airframes. Further, when it became clear that the a design flaw in the 737 rudder actuator had caused two fatal crashes, Southwest took years to replace them...they were the last carrier to complete the changes, and they lobbied the FAA hard to not make the actuator replacement mandatory....in other words, they fought to NOT replace the actuators.
However, the crew deserves kudos for safely handling the event. The Pilots responded promptly, professionally and capably.