More likely the speculation with the available funds.... Interest is rather just to have some "security".
I don't understand your posting. A German commercial bank can only make money in the interest business (customer deposits versus issuing customer loans and surplus investment in e.g. bonds) or in the commission business (fees / brokerage business, etc.). Only the banks that thought they had to play a big role in investment banking and invested in hocus-pocus securities were rescued. People scream when there is aid money, and they scream when there isn’t. But banks make money with interest. So what now? I myself am a small employee of a serious, well-running bank. We don’t have million-euro salaries like the investment bankers and constantly have to listen to cost reductions. Digitization, regulatory requirements (so many reports that cost a fortune) thanks to investment banks, millions of contributions to a default fund for the next crisis, etc. Yes, we earn more than many other industries. But you haven’t gotten anything for free for a long time. More and more is being cut, zero raises and reduction of jobs at the expense of the remaining colleagues. Think about that. By the way, recently the usury interest on defaults of tax offices was overturned. That is brazen.