After a life driven for the most part by fame, drugs, and his own ego, Bojack was changed by his time in rehab. He came out the other side trying to be a better person and genuinely improving his life.
This led him to accept a teaching position at Wesleyan University, something far from what he was used to in Hollywood. For once, instead of a narcissistic focus on himself and his celebrity status, Bojack Horseman honestly cared about the students he taught, and really tried to make them better actors.
So much so that when Princess Carolyn tried to poach one of his students and sign him to a big deal, Bojack passionately pleaded against it. He didn't want the fame and fortune to ruin the young man's life like it had his.
Even during his stint in prison at the end of Season 6, he still wanted to help people and pass on his craft to those around him. He took to putting on a production of Hedda Gabler with his fellow inmates, and once again, truly cared about his actors and making them better.
This standard nerd combines the looks of Shaggy with the brains of Scooby, has an unhealthy obsession with the Marvel Cinematic Universe, and is a firm believer that Alter Bridge are the greatest band in the world.