Italian banking, including the bank in question, got its start back in the middle ages by getting around prohibitions on usury with similar "guaranteed to lose" bets on currencies. The bank would give the borrower money in one currency now, and the borrower would give the bank back a different sum of money in another currency in 6 months. Given currency fluctuations, it was theoretically possible for the bank to lose the bet. Given the sums involved, this was very unlikely to happen in practice.

(Jews had the same commandment against usury, but interpreted it to only apply to other Jews. They could lend to Christians all that they liked, and did. That is where the connection between Jews and moneylending got its historical start.)

A lot has changed in the intervening centuries. The prohibition on usury was dropped, first by the Protestants and then by the Catholics during the counter-reformation. Banks have been regulated. And now the original workaround to allow loans at interest is seen as unacceptable. And so the Italian bank has been taken down by a deal that is very similar to the ones that got it started in the first place.