[solved] While doing the necessary detective work can be tedious and time-consuming, studying the strategies and situations of rival companies (most especially close rivals) well enough to be able to anticipate many of their next moves has the big advantage of

allowing company managers to accurately predict which rival companies are destined to gain market share and which ones are destined to lose market share over the next 3-5 years.

enabling managers to prepare effective countermoves (perhaps to even beat a rival to the punch) and to take rivals' probable actions into account in crafting their own best course of action.

helping company managers determine which rivals in other strategic groups need to be monitored very closely.

enabling company managers to determine which successful strategy elements of rival companies need to be quickly incorporated into the company's own strategy.

enabling a company to successfully underprice rival companies and steal away some of their sales and market share.