I don't know enough about color theory to really explain why this works so well, but there are plenty of papers and research on it.

Color is complicated.

- RGB is as simple but error-prone model for human color reception

- Human color reception is not linear and extremely lossy

- Color reception strongly depends on lighting and our vision autocorrects distortions

- Monitors and prints have their own quirks

As far as I know LAB color space tries to account for these facts. It doesn't surprise me that you found out that it worked better than other color models.