Produce a sentence which has a cefr level of "c1" and starts with: "large agencies "".
Large agencies "raided" smaller ones in hopes of luring away creative superstars with more generous salaries; they established more or less autonomous creative groups to produce material along DDB lines; they rejuvenated their management corps; and they leaped headlong into the endless theorizing about the nature of creativity that fills the advertising texts of the period.