We can see that the size of the quadrupole term becomes smaller. From 1% at l/d = 0.05 to 20% at l/d = 0.60. Thus, we can see that the size of the quadrupole term becomes significantly smaller if the nucleus decreases in size. Describing the nucleus by a point charge, if it is incredibly small does makes sense and thus it is logical that the quadrupole term starts to dissapear.