Disruptive selection tends to increase genetic variation.
In this case, Intermediates get deprived of the natural selection and on the contrary lives with high values and trait survive the chance of extinction. Consequently, changes start coming to the intermediates undergoing evolution to survive common problems that lead them to destruction
Understanding Disruptive selection by example and How it brings variety –
Suppose, There are three types of animal in a jungle. One is so powerful and that It hunts for living. And the other two animals are Herbivorous. But one of them knows to climb a tree, and the other one does not. So, sooner or later the animal which does not know to climb will extinct and another one that knows to climb a tree will survive.
Now there is a chance of genetic variation in that powerless animal like fast running or even climbing a tree. And if it happens, The chances of surviving through ages for them is expectedly high, and the new genetic trait will pass on through mutation. Also, It has gotten a greater reproductive success.