Not necessarily. Sometimes a large company (Hasbro) decides that instead of taking the time to form a team, create product, and hope it sells. To just buy an existing company (WoTC) for their share...there by getting into it on the cheap.
Also in some cases the parent company is smart enough to leave a successful team alone and are completely content to milk the cash cow. And in Hasbro's case make their extensive marketing and distrobution network available to the smaller organization. Being swallowed isn't always a bad thing...afterall you do get access to that companies coffers.