These “studies” aren’t worth anything. They examine and test one very narrow aspect of behavior and then declare their conclusions in very broad, sweeping statements that are applied far beyond what any reasonable person would conclude.
The conclusion “dumb flies live longer” is stupid. They have not made any fly more “intelligent”. They have subjected the flies to unnatural and unnormal trials which helped them pass “intelligence” tests, but detoured their small mental capacities from what they need to do for survival.
They have developed through selective breeding a strain of flies that learns quicker and retains memories longer.