We explain why the surprising one-loop finiteness of 6D half-maximal supergravities recently discovered in \cite{ Huang:2025nyr} is the result of the cancellation of the six-dimensional gravitational and gauge anomalies in (2,0) supergravity with 21 tensor multiplets and its anomaly-free SO(5, 21) duality. The one-loop finiteness of (1,1) supergravity with 20 vector multiplets is also explained by anomaly-free SO(4, 20) duality symmetry.
Categories: hep-th