only 1/40 th of the sunlight belongs to the blue part of the spectrum.
when the sunlight travels through the air it is scattered in all directions by the tiny particles in the atmosphere.
the blue light travels in shorter waves than the red, the yellow, the green...
the intensity of the light scattered by a particle is proportional to the inverse fourth power of the wavelength.
the blue wins. we see the blue. we see 1/40 th