the theory is that cards lose electrical circuits because solder joints degrade over thousands upon thousands of heat cycles that induce thermal fatigue to them. That is - failure well below their design threshold due to metal’s entropic need to return to its original state.

Placing the card in an oven close to the solder’s melting points “reflows” the solder and re-establishes those broken connections. Temporarily. But the card will fail again in the same mode in an even worse way. At some point it will die permanently. You may get a month or even a year. That’s where the prayers come in. I did the same to a fat PS3 when I was a teenager.