Uh oh. I suspect that the reason is that your climate is hard on them. In cooler, more equable, more humid climates, Fuchsias are more vigorous and and their pests less common.

Mealybugs are hard to deal with. They have a number of natural predators such as Cryptolaemus beetles and lacewing larva. Lacewings are pretty common; you might be able to find some.

Does the insecticidal soap claim to be effective on mealybugs? They might be somewhat resistent because of their fuzzy coatings.