If the fridge manufacturer goes bankrupt or changes how cold their fridge can get, I also go out of business in this contrived example. Do you also want to regulate these business decisions too? Shall the regulators intervene every time there is an ios update?
A better analogy is I produce aftermarket software/hardware for the refrigerator and want to force them to accommodate it (with the govt stepping in to determine which kinds of features they can and can't add on their own, e.g. browsers) and even sell it to customers for me.
As for your last question, the browser is the regulation. It is a very specific software product. In the case of apps, there is an open-ended range of function. Regulators must determine in detail which of these are to be protected. Presumably they must allow apple to block some apps like (easily-categorized) malware, but what about borderline and controversial decisions based on quality or ethics? Regulators are now deciding the detailed functionality of the product and preventing apple from differentiating their product. Shouldn't consumer choice be the deciding factor instead?
And as for browsers, again Microsoft was supposedly a monopoly. Not just their own niche store, but most of the entire market for OS's.
