Answer:
As it is known that the long legs of lizards are not advantageous or lost during the evolution which allows shorter legs will be evolved by some of the lizards and not by some others. The short leg lizards will evolve more than the average leg lizards due to the habitat of lizards which is an island and also helps in catching prey.
Another advantage of the short leg is the better grip to the branches so the natural selection takes place and the trait of the short leg which is advantageous increases over the average leg length lizards.