In my experience: ego. With few people you often have to keep things balanced and thus picking people that can work well with others. With 50, you are practically guaranteed to have at least several people that are absolutely insufferable(which can also happen in small teams in some cases - the reason why I resorted to "I quit, 1 month notice is best I can do, not 3, else I'll be doing the bare minimum for 3 months" at my old job). The truth is, more often than not, no one is willing to actively do anything about problematic people and hope that the problem will solve itself magically. Spoilers: it doesn't and it's not a question of if but when people will start quitting in swarms and usually that happens at the worst time for each company: heavy load, unreasonable deadlines, stress, etc. That's when you know the total collapse might be right around the corner.