Morshu originally sold items from a stand in a market. But then, Squadala Man placed an order for 10,000 bombs. Morshu became rich enough to buy a large building to house his store in. He made a business deal with Squadala Man so he could sell more bombs.
After Squadala Man captured East Hyrule, he let Morshu rule it. Morshu used this new power to make a chain of stores selling his goods all across East Hyrule.
Unfortunately, King Harkinian's men went in, and blew up the bombs in the stores, and there is only one again. People from all over the world come here for stuff.