The usual play is to acquire the customers and brand, with the team as a bonus.

Except for rare unique products, the source code might not matter at all. They're after the business, brand, and customers.

Having been in acquired SmallCos a couple times: There are always plans and justifications involving the products being acquired, but most don't survive impact with the acquiring company. People in a BigCo have their little fiefdoms established and everyone resists the sudden appearance of new developers and new code that weren't under their control. To be fair it goes both ways and the SmallCo developers who were previously in charge of everything don't like giving up control of parts of the system to the established teams and procedures in the BigCo.