Morgan Stanley, the biggest real estate investor among Wall Street banks, agreed to buy Richard Rainwater’s Crescent Real Estate Equities Co. for $2.78 billion. The $22.80 a share offer is 5.5% more than Crescent’s closing price yesterday. The total value of the transaction is $6.5 billion including debt, Fort Worth, Texas-based Crescent said yesterday in a statement. “Crescent has been a very troubled company over the years and it’s been a dramatically underperforming company,” the chief investment officer of realty funds at Cohen & Steers Inc., James Corl, said. “We have a saying that markets trump management, and their Texas office properties are in some tough markets.”