the only people willing to lend in Berkshire were in Kuwait and would only lend in dinars

In this context, "that" is used for emphasis. It's kind of like saying, 'Wow! *That* was a ____, wasn't it?' We use these kinds of sentences a lot, but mostly in spoken English. It's harder to recognize the meaning when you don't hear someone say it. It's a very common way of expressing our feelings about something that we think is amazing, crazy, horrible, or surprising.

They bought a bank in Chicago 30 or 40 years ago, it's name was Berkshire and it was located in Chicago ; but the only people willing to lend to the Berkshire bank were in Kuwait and and lent the bank in dinars rather than US Dollar.