So, in your opinion, the unsuccessful hair transplants are due to bad transplants (or the hair that was transplanted was also genetically programed to die)?
definitely. I am an "older" member on a hair transplant website and I have seen a lot of hair transplants stories (I mean real documented testimonies from day 1 to 12months and not videos from the clinics in 30sec).
Good hair transplants guarantee you decades of hairs. If surgeons take follicles in safe area (arround 5 cm wide) there is no reason the hairs fall. But of course you may lose little of density of the transplanted hairs over the years like most people. Just look at some older people without androgenetic alopecia , even with a solid looking norwood 1/mature hairline people often lose density naturally over the years.
on rarer occasions some younger guys who go for hair transplant might have thinning in donor area in the future but at the time they make the transplant we obv don't see it yet. same for retrograde but again you have to be unlucky.