Question

why equator receives comparatively less insolation than the tropics

Answer 1

equator receives less insolation than tropics as you all know that Insolation
is the amount of Sunlight received at the amount of the earth per unit area so the clouds obstructs the sunlight and hence equator receives less insolation .

generally the same latitude the insulation is more over the continent and over the Ocean because more clouds over the Ocean reflects and there's back into space for equator receives comparatively less insulation than the tropics