because they are russell 1000 index funds, so they must hold all these 1000 stocks in their fund. They can buy or sell more but must be within these 1000 funds. Get it ???
To prepare for the Russell 1000 index, Some analysts created bad news and stock was pushed down below 30 so big institutions can get cheap shares. Now they are done, stock price will move back up. Index fund managers of Russell 1000 must buy shares.