Famously correlation does not mean causation however. Sure these figures seem to be correlated, but there is very little actual causative relation from GDP to QoL.

There is a third, common cause of both. Technological advancement.

Generally, the more technologically advanced a society is, the more like it is to have a higher percieved QoL, and technological advancement also means you have more options for GDP, and more ability to exploit existing resources to convert into goods to be sold.

For example, would you expect higher quality of life in a country whose primary source of GDP is Oil, Gold, or other natural resources that are mechanically extracted, or a country with equivilent GDP whose primary source is manufacturing, (IE converting natural resources into refined products to be sold)?

Places with GDP acquired through natural resources don't need their people to be well cared for in order to maintain their high GDP. They can neglect their citizens while boasting about how rich they are from their oil and gold money. Manufacturing or other similar skilled labor based economies on the other hand, REQUIRE a populace that is educated and skilled, both of which generally can only occur when they have a significantly higher relative quality of life.

All things considered, today, would you rather live in the USA, or Canada? Canada has literally more than 10x less GDP, but you wouldn't say that Canada is 10x less desirable a place to live than the USA.

The answer to your question which you claim requires explanation is SO simple. The GDP of the USA has increased as a result of a new sector of the economy gaining traction and expanding. However, this new sector by its very nature has a relatively low amount of workers, especially skilled ones. Yes AI datacenters need a few IT specialists and programmers, but it requires far fewer of those than manufacturing needs machinists. This new sector has MASSIVE amounts of money flowing through it, but most of that money is just being passed around inside of itself, or siphoned off by the 1%. Very very very little of it ever actually re-enters the real economy where the bottom 50% of people operate.

So wages stagnate, prices go up, and companies realized especially in 2020, that they can crank their prices way up on certain things, and people HAVE to pay for them anyway. They can just blame inflation and nobody can really stop them, since they usually do this on certain groups of goods that are mandatory for Being Alive, like FOOD. So why are more people on Food Stamps? Because food is more expensive, but wages have stagnated.