It's not big goo. It's the explosion of artisan soaps with obnoxious fragrances and trendy labels.
A decade+ ago traditional wet shaving was much more niche and the traditional soap market was dominated by a few "household" names, mostly from Europe (largely Italy / UK / Germany / Spain). The US didn't really have much of a domestic shaving soap production. There were a few US options of course (not least Williams) but a lot of dedicated US wet shavers were buying imported soaps from Europe.
Wet shaving has grown massively since then, and a lot of that growth has been driven in the US and from a younger demographic than used to make up the traditional wet shaving market. We've seen an explosion in US artisan soap to supply that market, and because of the dominance of the US on social media due to sheer force of numbers, those are the soaps new shavers everywhere see and want. Now we have US artisan soaps being exported around the world, and local artisans popping up trying to imitate that kind of product (i.e. heavy fragrance / complex labels) which appeal to younger folks.
The result is that although the wet shaving market as a whole is so much bigger, the demand for traditional products is actually experiencing downward pressure, because it's only the older and value conscious folks that still want to buy the traditional soaps. Lots of us on B&B still like them, that's because we are attached to them from the time before these other soaps were available. Give a 22 year old with his new Henson a choice between MWF or something with a picture that looks like his favourite video game, and what do you think he is going to pick?
(Incidentally, this soap maker has a reputation for IP theft. It wouldn't surprise me if that image really is from a video game).
Of course, it doesn't help that a lot of them have seen reformulations that have negatively affected performance too. I think a few European countries with an established wet shaving culture (seems to be mostly Latinate countries - Italy, Spain, Portugal) have domestic products that will hold on, but even then we have seen stuff like Mogno go pop recently, LaToja cream discontinued, and now MWF gone for good. There's no guarantees!
That's my theory, anyway.
