The answer to 'why is my skylight cracked' is that skylights can crack for a few common reasons. Skylights are exposed to the elements and can become damaged over time due to weather, age, or impact. Some of the most frequent causes of cracked skylights include hail damage, heavy snow or ice buildup, and thermal expansion and contraction from temperature changes.
If you notice a crack in your skylight, it's important to address it promptly to prevent further damage and potential leaks. Small cracks may be able to be repaired, but larger cracks or extensive damage will likely require the skylight to be replaced. In some cases, the underlying frame or flashing may also need to be repaired or replaced. It's generally best to have a professional roofing contractor evaluate the damage and provide the appropriate solution.