Understand Mulch Decomposition and Fabric Failure

What happens here

Understand the fundamental reason why landscape fabric under mulch is ineffective. Mulch, being organic material, naturally decomposes over time, breaking down into a fine soil-like substance. When landscape fabric is present, this decomposed mulch accumulates on top of the fabric, effectively creating a layer of new soil. Weed seeds, which are ubiquitous in the environment, can then land on this new soil layer above the fabric, germinate, and grow roots into it, making the fabric redundant. This creates a difficult-to-manage 'Oreo' effect with soil, fabric, and more soil.

Goal: Grasp the mechanism behind weed growth in mulched areas with landscape fabric.