To catch more fish, the simplest thing to do is put out more pots. That is exactly what happened and, since people were making good money fishing, more people became fishermen. Take a look at this figure which shows the amount of all kinds of fish reported as caught by the fishermen. The first thing to note is the dramatic increase in the amount of fish caught in the early 1980's due to the increased effort by the fishermen. Clearly they were successful for a short time.
Lets look at the same data but in another form.
This figure shows the amount of two kinds of fish caught in each trap. You can see that the number of groupers in each trap had been dropping from 1975 when data was first collected and the amount of other reef fish was increasing during the time when the total amount of fish was increasing. If you add the data for the two kinds of fish together, you get the data in the first figure. So what if it became more difficult to catch fish, just keep putting out more pots. That's where an understanding of the ecology of the reef is important.