Charles quitting is grossly exaggerated
Part of it came from a fight where he tore his esophagus and literally his life was in danger
As he filled out his frame he became very durable.
Most guys aren't fighting elite UFC guys from age 20.
Oliveira had to learn on the job and did it at a very very high level, fighting guys like Pettis, Holloway, Jim Miller, Frankie Edgar and Cowboy. Dude jumped straight into the shark tank
Most guys go thru those fighter "life lessons" in a regional org, and you can GET AWAY with an off night at that level. Charles was facing superstars and Killers pretty much from the jump in his UFC career. Cub Swanson, Jeremy Stephen's, Brookins even Darren Elkin, that's a tough run not to mention the occasion champ/challenger tier guys he got thrown in with even early on