Or the whole thing is a deliberate troll and he's an entirely different bloke called Isildur.
They have messed with the timelines so much then it could be the "real" Isildur. He was born in the second age in SA 3209, son of Elendil and founded Gondor albeit around SA 3500 . Numenor is destroyed by the great flood in SA 3320 and we know Amazon plan on covering that as that is the vision the Queen keeps seeing which is 2320 years later than the period we are in now. Plus Isildur was around 250 years old when the Orcs shot him with the ring so Amazon can play around with people living centuries.
I mean Morgoth made Mount Doom in the first age but what are Amazon going to do? Once Sauron makes his base in Mordor in SA 1000, he basically stays there for 2500 years with nothing much happening.
To be honest I am currently lost as to what year we are meant to be in at the moment. Looking at Isildur we should be around SA 3230 ish. But if it is then Sauron has been living in Mordor for 2230 years already and has already built Barad-dûr and the black gate and the Rings of power including the One Ring have been in existence for over 1600 years.
So none of it makes sense. Best to just ignore what Tolkien wrote and enjoy the show.