It is worth noting that measures of quality of life are often conflated with wealth, even to a degree that they quite often use straight up economic metrics (like GDP) in their models.
On top of that our global capitalist situation heavily favor exploitation in cheaper labor markets. So if you are a millionaire CEO in a rich country you are very likely to exploit your workers in poorer countries (or more likely, the workers of your providers and contractors) which overall increases the QOL in your country while decreasing it in your worker’s country. Your correlation might be a cross causation.
On top of that our global capitalist situation heavily favor exploitation in cheaper labor markets. So if you are a millionaire CEO in a rich country you are very likely to exploit your workers in poorer countries (or more likely, the workers of your providers and contractors) which overall increases the QOL in your country while decreasing it in your worker’s country. Your correlation might be a cross causation.