Not only do institutional investors not engage in so-called “arbitrage”. They even increase “mispricing” and increase the market failure, just not as much as retail investors do. It's not “smart money vs. dumb money”, it's “dumb money and dumber money”.
Firms and short sellers tend to be the smart money—both sell stocks with low expected returns, and their trades predict returns in the intended direction. Firms, however, also seem to possess private information, while short sellers do not. Retail investors buy (sell) stocks with low (high) expected returns and their trades predict returns opposite to the intended direction. All 6 types of institutional investors are weighted towards stocks with low expected returns, but none of their trades robustly predict returns.
Only the short-sellers as a whole are the smart people in the room.