If the industry they work in can't compete their entire income is reduced to zero.
That can knock out related industries as well and ultimately leave the country exposed to currency collapse and hyperinflation as the exporting countries decide that this country has nothing it really wants any more while they still desperately need imports.
This happened to Venezuela (after local industrialists declared war on Chavez in 2002 he effectively set out to destroy them) and Zimbabwe (when Muagabe dispossessed farmers from their land, rendering it unproductive).
The US is also exposed to this risk. It's steadily but very slowly losing hi tech manufacturing capabilities - something that takes decades to get back once lost (due to the network effect and loss of skills).
But I thought we're talking about a time period before that industry even exists.
Like coffee, I believe the industries that are able to produce higher quality beans with more equitable and fair labor practices are doing better than the countries that continue producing cheap cacao. Something that I am under the impression is less supported by European chocolate producers.
My source is my time as a chocolate maker in the US.