Fit off the court
Playing in Los Angeles demands huge attention off the court. LeBron is a superstar that also commands huge attention. Combined these two factors an everything you do on and off the court everyone will be watching you if you would play for Lakers.
As an organization, you need to have a stable locker room if you want to compete to a championship, but in the case of the Lakers, you need a solid profound locker room that no matter what they can continue playing well.
The Lakers have three young players in Lonzo Ball, Kyle Kuzma, and Brandon Ingram that are adapting to the life of the NBA and the life of living in LA, and all of them need a veteran player with huge experience that they can depend on. Horford has huge experience playing in more than 100 games in the playoffs throughout his all career.