Your claim is simply false.

The 2nd law of thermodynamics says that the total entropy of an isolated system cannot decrease. Earth is not an isolated system, it is an open one (radiating into space), and local decreases in entropy are not only allowed but expected in open systems with energy flow.

Life is no different to inorganic processes such as crystal formation (including snowflakes) or hurricanes in this regard: Organisms decrease internal entropy by exporting more entropy (heat, waste) to their surroundings. The total entropy of Earth + Sun + space still increases.

The entropy of thermal radiation was worked out by Ludwig Boltzmann in 1884. In fairness to you, I suspect most people wildly underestimate the entropy of thermal radiation into space. I mean, why would anyone, room-temperature thermal radiation isn't visible to the human eye, and we lack a sense of scale for how low-energy a single photon is.

Nevertheless, the claim that it "hasn’t been explained" is, at this point, like saying "nobody knows how magnets work".