The answer to 'why is my mulch mud' is that your mulch has become oversaturated with water, causing it to turn into a muddy, sloppy mess. This can happen due to heavy rainfall, poor drainage, or excessive watering.
Mulch is designed to help retain moisture in the soil and suppress weeds, but too much moisture can cause it to break down and become compacted, leading to a muddy, mucky appearance. This can also lead to issues like mold growth, plant disease, and poor aeration for your plants' roots.