The fundamental reason behind most acquisitions when an exit of some kind is the ultimate goal is the concept of multiple arbitrage. Put simply, this is the practise of increasing the value of a company without having made any operational improvements to it. This is achieved by acquiring a company for a lower multiple than you believe the consolidated group will be able to exit for. For example, if you believe that as a larger group, you should be able to exit for 10x EBITDA but can make an acquisition of a company for 6x EBITDA, then the new company instantly creates value for you to the tune of the delta between the two multiples.
Done correctly, multiple arbitrage can be used to generate a positive impact even before making a single cost cut or realising any synergies. However, it does hinge on finding the right company/companies to acquire and being able to accurately perceive valuation.