The answer to 'why is my landscape lighting disease' is that there are a few common causes for landscape lighting issues, including wiring problems, fixture damage, and power supply issues. Symptoms may include lights flickering, not turning on, or only partially working. To troubleshoot and fix the problem, you'll need to inspect the wiring, check the transformer and connections, and replace any damaged fixtures.
In many cases, landscape lighting issues can be resolved with some basic DIY troubleshooting and repairs. However, if the problem persists or you're not comfortable working with electrical systems, it's best to call in a professional landscaping or electrical contractor to diagnose and fix the issue properly.