Because the sun is an enormous sphere of hydrogen-helium plasma with a core that's undergoing fusion just due to gravity. Even indirect sunlight is still a very large amount of light and energy.
I don't mean to sound flippant, but I think sometimes people forget just how insanely energetic stars of all sizes are.
I don't mean to sound flippant, but I think sometimes people forget just how insanely energetic stars of all sizes are.