I believe professional investors who manage Other People's Money are similar in their mindset and actions as those who paper trade. Both take excessive risks because they know any losses will be shifted onto others or are fictitious. Moreover, since they don't suffer any personal losses, they can become overconfident and sloppy in their trading. They take excessive risks either to try to beat the market and earn out-sized profits or to gain confidence in coming up with a trading strategy.
1) Most money managers are content to be mediocre and avoid excessive risk just to earn management fees, not performance fees. 2) With paper trading, you can do any "imaginary" stuff you want with no regard for "consequences".