It's a step by step process.

Some automotive jobs are a simple in and out fix for a vehicle. But sometimes when working on a vehicle there can be steps to take to eliminate or sometimes even diagnose issues. Electrical issues and oil leaks can be two major examples. Sometimes when eliminating one leak by removing an item to replace a seal, another leak can be spotted BEHIND that one that couldn't be seen earlier. In some cases pressure flow can be less due to a leak. When pressure returns to the line due to fixing the original issue then other weak areas can break due to pressure returning to the area.