There aren't actually that many people who can afford Afghan Bagel. Shops catering to niche interests mostly get started because the owners overestimate their chances of success. They try to attract customers for a few months but fail to turn a profit and eventually close the shop. The landlord doesn't care, because there will always be another fool with more dreams than business sense.

In my neighborhood, all kinds of hip coffee shops and boutiques keep opening and close just as fast. The only ones who hold out for longer have been there for decades, so they're probably protected by the cap on rent increases. It also helps to be an ordinary baker rather than specializing in Afghan Bagel, because that way they can get enough customers to keep the business afloat.