Crown of thorns seastars are a normal, natural predator on these reefs.
Their primary predator, the triton trumpet snail, is/has been harvested for the shell trade in large numbers. It is a huge snail (it is a huge star) and takes a long time to grow.
There are normal cycles in nature...at times reefs may be dominated by algae, and fast growing corals...when grazers are low. When there are a lot of grazers, slower massive corals may dominate. Taking cores through fossil reefs, often these phases are very clear. They may occur naturally, or may be the result of human activity or "doing the right thing" interference without understanding what we are doing. People can make the "wrong" decisions because they feel that certain animals are nicer, prettier, and others are mean.
A classic example is the urchin Diadema that used to be in huge numbers on Caribbean reefs. They had several setbacks, including a few hurricanes, but several decades a go a mysterious disease seemed to wipe out huge numbers. They are not longer anywhere near as common as they once were. And as a result, many carribean reefs are dominated by fast growing corals, and algae (this is not to say there are no massive slow growing corals...)
With Acanthaster, the crown of thorns, there are normal cycles of survival. But as noted, there is a major issue with run off of nutrients from farming and logging practices. This results in increased success of the larvae, and ultimately, adults.
I am typically wary of human intervention at the stage they are doing it. The real focus, money and effort needs to be put into changing the nutrient input. In and of itself it can be a problem to reefs. I think the effort is slightly misguided, though short term and localized, it probably works in areas. But I think they need a somewhat different long term plan.