The short answer is the movie doesn't reflect real life events in this case. Rather than die shortly after the incident as depicted by the movie, Ryan Job was actually discharged from the Navy, got married, and passed away over two years later due to complications from facial reconstructive surgery. This is mentioned in multiple articles comparing the movie to the book/real life.
Did Ryan "Biggles" Job only survive for a short while after being blinded by a bullet?
No. In the movie, Ryan "Biggles" Job (Jake
McDorman) is blinded by Syrian sniper Mustafa. He survives for a short
period of time and proposes to his girlfriend while in the hospital.
Kyle visits him shortly before leaving for his fourth tour and learns
of Ryan's death just after he arrives back in Iraq.
In real life, Ryan was blinded in battle in 2006 when an enemy
sniper's bullet struck his rifle, sending pieces of the shattered
weapon through his face. He survived much longer than he does in the
movie. He was discharged from the military, got married, attended
college, got a job, climbed Mount Rainier and Mount Hood, etc. He died
in 2009 from complications after going back for more facial
reconstructive surgery while his wife was pregnant with their first
In the movie, Ryan Job (or “Biggles,” played by Jake McDorman) is shot
in the head and blinded by Syrian sniper Mustafa but survives long
enough to propose to his girlfriend. He dies soon after, and that
death defines Kyle’s fourth tour in Iraq and spurs him to seek revenge
against Mustafa. In reality, according to Kyle’s memoir, the Navy
discharged Biggles from service following his injury. The ex-SEAL
attended college, began a career, and got married before dying
following facial reconstruction surgery while his wife was pregnant
with their first child.
An obituary piece for Ryan Job can be found here, highlighting his many accomplishments after his discharge from the Navy.