Why is Jupiter sometimes considered a “failed” star?

Jupiter is a huge, rapidly spinning liquid ball topped by a thick atmosphere composed mostly of hydrogen and helium. It seems to have a relatively small iron silicate core. Jupiter is more massive than all the other planets and their moons combined. Nuclear fusion reactions in the interior of Jupiter would begin if its mass were 12 times greater (these are short-term conditions for the combustion of deuterium). If the mass of Jupiter is “increased” by 80 times, conditions would arise for the proton-proton cycle of nuclear reactions (as in the interior of the sun).