The equilibrium in random mating population is disturbed by selection, mutation, inbreeding, migration and genetic drift in which situation the population may regain its original composition

The equilibrium in a random mating population is disturbed by the selection, mutation, inbreeding, migration, and genetic drift in the Selection situation the population may regain its original composition.
Natural selection and non-random mating disrupt the Hardy-Weinberg equilibrium because they result in changes in gene frequencies. This occurs because certain alleles help or harm the reproductive success of the organisms that carry them.
Random mating prevents allele frequencies to change, while genetic drift and natural selection do the opposite.