Citicorp could have agreed to market Travelers insurance or Salomon brokerage services, and vice versa, without actually becoming one company.
Citicorp did not want to market the insurance companies. 
mnli hypothesis: Citicorp did not want to market the insurance companies.  premise: Citicorp could have agreed to market Travelers insurance or Salomon brokerage services, and vice versa, without actually becoming one company.