Stress is the enemy of fish health. Cryptocaryon will target stressed fish with lowered immune systems. Anything we can do to reduce the stress that fish undergo will decrease both the disease incidence, mortality, and improve treatment results. Remember that almost all marine fish are wild harvested and are extremely stressed by the time they reach your home. These fish need to be handled very carefully to avoid disease outbreaks. They need to have perfect water quality, correct nutrition, a stable temperature, and places to hide and feel secure. If any of these needs are not met, then the already stressed fish will likely develop marine ich or another disease.
This is straight from the article you just sent me ,it also stated that ick is in the ocean but because the fish are in the ocean it's at a much lower concentration for the parasite to attach to the fish ,in the home aquarium the concentration is way higher