Radius is not mass
A red supergiant can have a radius hundreds of times the Sun while having a mass only tens of times the Sun or less after mass loss.
That means the outer envelope is extremely diffuse. Big does not mean dense.
Brightness is not apparent brightness
Luminosity is the total energy output. Apparent brightness is how bright a star looks from Earth, which depends strongly on distance and dust.
Rigel is one of the brightest-looking stars in the night sky because it is both very luminous and relatively nearby on galactic scales.
Use the tool on the homepage
The homepage comparison tool uses conservative ranges for well-known supergiants. It is built to teach proportions, not to claim permanent record values.