If a company has monopolises a certain industry, market or brand it’s going to be highly associated with it, especially with little to no competition. It’s like the thing with Harlequin where they have a near monopoly on the romance market and even bought some of its competitors. DC and Marvel hold a duopoly on superhero stories.
That’s not to say this hasn’t been done to other storytelling modes, maybe not to the same extent. As for science fiction there’s Gollancz, Penguin Random House, Macmillan, Harper Collins, Orbit Books, Arkham House and if you will, Games Workshop as it also publishes prose books.
I could also say similar things about Hasbro’s Wizards of the Coast in relation to fantasy. So there’s a healthy amount of competition but they may also constitute a near disproportionate number of publishers making a lot of those books. Fashion likely does similar things. Around 20% out of 500 companies make a lot of profit.
Many of the luxury conglomerates used to be entirely separate companies. They may have a lot of competitors (perhaps same with their fast fashion counterparts) but when they often risk being bought by either one of them, it’s like they don’t want much competition.
Even if supermarkets/malls may have their own in-house clothing lines and if some fashion companies remain independent whether big or small, same with textile manufacturers but when mergers and buyouts occur in addition to facing increased competition by imported brands that it’s going to be tough to stay afloat.
Let alone on its own that being bought by another or merged’s one of those ways to expand.