It took a while for the water to get clear into the drywall. In the process, water had to leak through studs, insulation, and other barriers, leaving moisture damage through and through. That means in the cavity of the wall, there is great opportunity for microbial action, and continued rotting inside. Also, if you ‘plug’ one leak on the exterior, you are likely to just divert the water into another area that is also deficient, and another leak will occur. I often hear, “I had a leak over here and fixed it, but now there’s a new one over there.” Taking the time and effort to correct a deficiency will save you time, money, effort, and headaches down the road.